GIFT  OF 


of  the  Department 
OF 

antf  f 


THE  AMERICAN 
Thompson  Improved  Exposed  Spring  Indicator 

with  the 

New  Improved  Detent  Motion 


TWENTY  YEARS 


WITH   THE 


INDICATOR. 


BEING   A 


PRACTICAL  TEXT-BOOK  FOR  THE  ENGINEER  OR  THE  STUDENT, 

WITH    NO   COMPLEX    FORMUL/E. 


With  many  illustrations  and  rules  as  to  the  best  way  to  run  any  Steam  Engine  to  get  the  moat 

economical  results.     How  to  adjust  Valves  and  Valve  Motions  correctly.     Full  directions 

for  working  out  Horse  Power \  the  amount  of  Steam  or  Water  per  Horse  Power,  Econ- 

trtny  of  Fuel.      The  author's  original  and  correct  application  of  the   Theoretical 

Curve,  to  show  exactly  where  the  steam  valve  closed,  and  whether  valves  leak 

or  not;  extended  directions  for  attaching  the  Indicator,  what  motions  to 

use  and  those  not  to  use.       Full  directions  for  computation 

of  Power  by  Planimeter  and  other  methods. 

with  many  tables  and  hints. 


NEWLY  ARRANGED  AND  COMPLETE  IN  ONE  VOLUME, 

TWENTY-FIRST  THOUSAND 


BY  THOMAS   PRAY,  JR., 

CONSULTING  AND   CONSTRUCTING  AND    CIVIL    AND    MECHANICAL   ENGINEKK, 
MEMBER    OF    VARIOUS    SOCIETIES,    ETC 


BOSTON : 

AMERICAN  STEAM  GAUGE  AND  VALVE  MFG.  CO. 
208-220  CAMDEN  STREET. 

1909. 


Engineering 
Library 


VOL.  I. — COPYRIGHT  1882. 

COPYRIGHT  AND  ALL  INTEREST  TRANSFERRED  TO 

THOS.  PRAY,  JR.,  1885. 


VOL.  II. — COPYRIGHTED  1885,  BY 

THOMAS  PRAY,  JR.,  BOSTON,  MASS. 

ALL  RIGHTS  RESERVED. 


BOTH  VOLUMES  IN  ONE. 

COPYRIGHTED  BY  THOMAS  PRAY,  JR. 

BOSTON,  MASS. 

1888. 


COPYRIGHT  AND  ALL  INTEREST  TRANSFERED  TO 

AMERICAN  STEAM  GAUGE  AND  VALVE  MFG.   Co. 

208-220  CAMDEN  STREET, 

BOSTON,  MASS. 

1908. 


PRESS  OF 

A.CHEY    &    GORRECHT 
LANCASTER,  PA. 


DEDICATION  OF  VOL  I. 


THIS  work  is  respectfully  dedicated,  with  the  highest  feelings  of  regard,  to 
my  friend,  J.  M.  ALLEN,  of  the  Hartford  Steam  Boiler  Insurance  and  Inspec- 
tion Company,  for  his  high  value  of  personal  integrity,  and  for  the  good  he 
has  done,  and  is  doing,  to  protect  the  lives  of  stationary  steam  engineers  and 
the  property  in  their  and  his  charge, 

BY  THE  AUTHOR. 


DEDICATION  OF  VOL  II. 


THIS  volume  is  dedicated,  with  every  sense  of  respect  and  the  highest 
regard,  to  that  class  of  men  who  are  everywhere  working  to  better  inform 
themselves,  to  better  their  condition  by  knowledge  and  fidelity,  and  to  secure 
greater  safety  in  the  steam  power  in  their  control,  and  consequently  better 
results  to  their  employers,  and  greater  safety  to  human  life  everywhere — 
THE  WORKING  ENGINEERS— Marine,  Locomotive  or  Stationary—wher- 
ever they  are,  in  the  humble  hope  that  it  may  contribute  to  their  benefit, 
from  an  extended  experience  of  one  who  is  practically  one  of  them. 

THE  AUTHOR. 

JANUARY  1st,  1885. 


274759 


PREFACE  TO  VOL.  I. 


WHEN  the  author  commenced  a  series  of  articles  on  the  Indicator  in  the 
BOSTON  JOURNAL  OF  COMMERCE,  it  was  only  with  an  idea  of  writing  a  few 
articles  in  number,  for  the  purpose  of  showing  up  some  of  the  most  generally 
found  defects  oi  the  builders  of  steam  engines,  —  defects  in  practice,  —  and  to 
explain,  in  as  simple  a  way  as  possible,  how  to  adjust,  or  at  least  how  to  over- 
come these  defects,  so  far  as  the  defects  of  building  would  allow,  and  make  a 
more  economical  use  of  steam.  The  subject,  however,  grew  on  the  author's 
hands,  and,  rather  to  his  disappointment,  a  great  deal  of  inquiry  was  elicited. 
The  articles  were  continued  far  beyond  his  own  ideas,  originally,  and,  as  the 
paper  was  growing  rapidly  in  circulation,  hundreds  of  subscribers  were  added 
who  could  not  procure  the  first  of  the  series.  Within  the  first  four  or  five 
months  inquiries  began  to  come  in  asking  us  if  we  would  not  print  the  articles 
in  book  form.  It  was  a  year  or  more  after  the  appearance  of  the  first  article  of 
the  series  before  time  could  be  given  to  their  revision  for  the  purpose  of  re- 
publication  in  book  form.  Meantime  the  name  of  the  paper  had  been  changed 
to  COTTON,  WOOL  AND  IRON,  and  the  subscription  list  was  increasing  faster 
than  ever.  All  this  required  new  quarters,  and  we  were  obliged  to  move  in  the 
very  midst  of  the  preparation  of  this  book ;  and  the  book  was  still  further  de- 
layed some  two  or  three  months  on  account  of  having  to  add  to  our  plant  for 
printing  the  paper.  This,  in  brief,  is  how  this  book  came  to  be  printed.  It  is 
offered  to  the  public  with  the  full  knowledge  that  there  are  many  little  inac- 
curacies, arising  from  the  fact  that  the  author  has  been  doing  the  work  of  two 
or  three  men.  Aside  from  having  the  full  management  and  editorial  charge 
of  the  paper,  (which  is  no  easy  job,)  his  daily  consultations  have  been  large, 
being  obliged  at  times  to  travel  several  hundred  miles  per  week,  which, 
together  with  the  charge  as  consulting  engineer  of  a  number  of  large  steam 
plants  and  cotton  mills,  has  made  it  next  to  impossible  for  him  to  sit  down  for 
more  than  an  hour  without  interruption  or  being  obliged  to  drop  the  work 
entirely  for  days  together. 

The  subject-matter  of  the  book  has  been  gathered  from  probably  the 
broadest  experience  ever  enjoyed  or  earned  by  any  man  in  this  country.  It 
was  commenced  at  a  time  when  but  very  few  people  knew  anything  of  the 
Indicator,  and  the  instrument  was  in  a  crude  state,  —  when  it  was  far  from 
perfect.  The  hobbies  and  vagaries  of  engine  builders,  the  ignorance,  preju- 
dice, and  love  of  the  dollar  on  the  part  of  the  steam  users,  and  the  bigotry  and 
prejudice  of  the  working  engineer,  made  it  at  times  almost  impossible,  even 
when  we  were  investigating  for  our  own  benefit,  to  obtain  access  to  an  engine. 


PREFACE.  v 

But  gradually  questions  arose  which  compelled  some  arbitration  ;  we  were 
fortunate  enough  to  be  appointed  by  the  Supreme  Court  of  several  States  to 
carry  on  investigations,  which  opened  up  such  questions  that  the  steam  user 
and  the  engine  builders  were  obliged  to  make  a  limited  use  of.  the  Indi- 
cator. Meantime  the  change  in  engineering  has  called  for  a  broader  use  of 
the  Indicator,  has  called  for  more  knowledge,  and  that  this  knowledge  shall 
be  based  upon  fact.  The  makers  of  the  instrument  have  kept  pace  with  the 
requirements  of  the  engineering  profession,  and,  without  doubt,  the  Ameri- 
can Indicators  of  to-day  surpass  everything  made  in  the  world  before,  for 
their  accuracy,  and  their  durability  under  all  the  range  of  requirements 
from  the  slow  moving  low  pressure  engine,  to  the  high  speed  and  high 
pressure  locomotive,  and  electric  light  engine. 

The  lessons  in  this  book  are  drawn  from  actual  practice  ;  with  very  few 
exceptions  the  diagrams  were  all  taken  by  our  own  hands.  What  this  labor 
has  cost,  no  one  but  ourself  can  properly  understand.  At  times  working  all 
night,  and  not  in  the  pleasantest  quarters — sometimes  without  anything 
beyond  the  crudest  tools — in  attempting  adjustment  where  the  builder  of  the 
engine  had  absolutely  precluded  any  adjustment ;  working  against  all  the 
different  degrees  of  prejudice  and  ignorance,  frequently  going  without  food 
for  many  hours  together,  being  compelled  in  a  certain  time  to  accomplish  all 
that  could  be  done  ;  making  long  railroad  rides  at  night  ;  working  all  day 
and  night  — all  this  has  not  been  pleasant,  but  it  has  brought  about,  to  a 
great  extent,  a  revolution  in  the  practice  of  the  Indicator,  and  an  amount 
of  information  of  easier  access  to  the  reader. 

These  pages  are  offered  with  a  full  knowledge  of  their  faults,  but  it  has 
been  the  author's  intention  to  convey  knowledge  to  the  greatest  extent  pos- 
sible, and  in  such  a  way  that  the  working  engineer,  and  the  men  who  use 
engines,shall  understand  them  and  be  able  to  work  out  their  own  adjustment, 
if  they  will  but  give  a  little  time  and  patience  to  it.  The  second  volume  will 
contain  more  extended  information  with  reference  to  the  theory  of  working 
steam,  and  the  application  of  general  rules  as  to  the  measurement  of  steam 
and  water,  with  some  curious  illustrations  from  actual  practice,  of  the  vaious 
ways  of  connecting  the  Indicator  to  the  cylinder,  errors  in  motions,  and  a 
variety  of  matter  which  is  not  yet  fully  laid  out.  Inquiry  has  at  this  time 
taken  a  turn  toward  adding  something  in  reference  to  combustion  and 
various  boiler  settings,  and,  if  we  follow  the  subject,  it  will  probably  run 
into  the  third  volume.  The  second  volume  will  be  issued  sometime  within 
a  year,  and,  as  to  the  third  volume,  much  will  depend  upon  our  personal 
arrangements,  how  much  can  be  done,  and  how  much  time  we  can  give  to  it. 

The  diagrams  in  this  work  are,  in  in  every  case,  full  size,  so  they  can  be 
measured  and  worked  from  accurately,  or  a  tracing  can  be  made  for  that 
purpose.  In  every  case  our  aim  has  been  to  give  the  facts,  and  wherever  the 
name  of  the  builder  has  been  mentioned,  it  is  not  with  any  intention  of  either 


vi  PREFACE. 

recommending  or  disparaging  his  or  their  work.  The  names  are  used  only  as 
the  types,  and  in  many  cases  where  bad  adjustment  has  been  shown,  it  has  not 
been  any  fault  of  the  builder.  In  other  cases  this  cannot  be  said.  The  book 
is  from  a  practical  experience,  with  all  the  ins  and  outs  that  are  liable  to  occur 
in  a  large  practice.  We  only  regret  that  other  duties  absolutely  forbid  our 
giving  practical  attention  and  time  to  the  calls  which  are  now  made  upon  us, 
otherwise  we  might  soon  issue  a  second  volume,  which,  while  not  containing 
so  much  in  breadth  or  in  fact,  could  be  made  more  elaborate,  and  perhaps 
more  practical  and  interesting. 

THOMAS  PRAY,  JR. 
Boston,  January  3,  1883. 


Since  the  publication  of  Vol.  I.  [first  edition]   all   interest  in  the 
publication  and  the  copyright  have  been  legally  transferred  to  me. 

THOMAS  PRAY,  JR. 

July,    1887. 


PBEFACE  TO   VOL.  II. 


As  announced  in  Vol.  I,  this  book,  Vol.  II,  is  launched,  not  as  a  literary 
effort  or  a  scientific  essay,  but  rather  as  a  practical  hand-book  or  text-book  for 
the  working  engineer,  the  steam  user  or  any  who  may  be  learning  something 
as  to  the  construction  of  engines  and  what  constitutes  the  economy  of  an 
engine,  what  use  is  made  of  the  steam  after  being  produced  by  the  boiler, 
and  whether  this  use  is  good,  bad  or  indifferent.  The  book  has  not  a  single 
mathematical  formula,  algebra  and  the  higher  mathematics  having  been 
entirely  left  out ;  not  because  the  engineers  could  not  understand  them,  for 
many  of  them  are  capable  of  understanding  the  higher  mathematics,  as  we 
know,  and  very  many  make  regular  use  of  formulae  in  their  calculations  for 
the  sake  of  brevity.  We  have  ourselves  had  no  difficulty  in  expressing  any- 
thing in  few  words  without  resort  to  formulae  ;  and  as  so  many  of  our  engi- 
neers have  graduated  from  the  fire  room,  and  then  taken  positions  in  the 
engine  room,  or  in  charge  of  both,  who  have  had  no  chance  at  even  common- 
school  education,  we  have  preferred  to  put  everything  in  the  plainest  word- 
ing, so  that  all  might  thoroughly  comprehend  and  avoid  any  confusion  or 
misunderstanding.  So  much  for  the  general  character  of  the  work. 

This  work  has  been  compiled  from  one  of  the  most  extensive  practices 
any  man  was  ever  engaged  in,  at  a  time,  too,  when  the  author  has  been  not 
only  busy  but  a  very  busy  man.  Much  of  the  work  has  been  done  "  atween 
times,"  or  when,  for  his  own  comfort,  he  might  have  been  resting,  and  all  the 
time  during  the  progress  of  the  work,  which  has  been  slow,  and  interrupted 
twice  for  several  months,  he  has  been  busy  with  a  large  consultation  practice, 
with  the  cares  of  a  paper,  and  other  matters,  so  that  Vol.  II  has  been  delayed 
many  months  longer  than  was  expected. 

The  subject  matter  of  Vol.  II  is  very  largely  new,  only  a  few  articles 
having  been  reproduced  from  the  columns  of  the  Manufacturers'  Gazette, 
and  in  every  case  these  reproductions  have  been  made  use  of  from  radical 
points  either  of  misuse,  misconstruction,  or  some  other  peculiarities  which, 
while  all  too  frequent,  we  are  not  always  able  to  lay  our  hands  upon  for 
ready  reference.  The  various  uses  of  steam  cover  a  broad  ground,  from 
the  last  new  ocean  steamship  to  the  15  horse-power  high-speed  motor  for 
electricity.  All  through  the  work  the  author  has  endeavored  to  avoid  any 
personal  reference,  or  to  revive  any  criticisms  other  than  so  far  as  principles 
of  mechanism,  or  a  wasteful  use  of  steam  were  concerned.  Trials  of  engines 
have  been  for  the  information  of  the  reader ;  trials  of  indicators  have  been  to 
obtain  absolute  information  for  our  own  use,  and  in  these  cases  all  have  been 
judged  by  the  inflexible  standard  of  right,  without  regard  to  the  assertions 
of  the  several  builders,  patentees,  improvers  or  venders,  meaning  to  place  on 


viii  PREFACE. 

record  only  those  facts  •which  were  of  importance  in  the  use  of  thia  much- 
abused,  much-misunderstood,  and  yet  so  simple  and  accurate  an  instrument 
as  the  steam-engine  indicator.  A  large  majority  of  the  diagrams  in  this  vol- 
ume have  been  taken  by  the  author's  instruments  and  hands.  It  has  been 
the  aim  to  avoid  repetition  and  to  introduce,  as  much  as  was  possible,  all  the 
conditions  of  adjustment,  whether  right  or  wrong,  of  construction  or  of  fancy 
that  might  possibly  arise  upon  any  engines,  anywhere,  in  any  kind  of  service, 
so  that  the  book  might  become  more  valuable  to  those  who  were  far  away 
from  the  builders  of  engines,  and  to  make  it  all  the  more  valuable  to  them 
as  affording  away  out  of  any  trouble  into  which  they  might  be  thrown. 

The  extremely  .extended  use  of  the  steam-engine  indicator  within  the 
last  four  or  five  years,  has  called  for  some  book  from  a  practical  man,  which 
should  not  in  any  case  toady  to  the  indicator  builders,  except  to  apply  their 
instrument  when  it  was  reliable,  and  would  record  in  such  a  manner  that  the 
diagrams  were  of  some  practical  value  to  the  men  who  are  not  thoroughly  up 
in  a  wide  practice.  It  has  also  been  the  aim  of  the  author  to  be  all  the  more 
guarded  in  offering  instruction  which  should  be  of  benefit  to  the  only  men 
for  whom  we  are  writing  in  general,  viz.,  the  party  who  owns  the  engine  and 
the  working  engineer  in  charge  of  it,  so  that  these  two  men  should  be  entirely 
free  from  the  assumption  so  frequently  imposed  upon  them  by  ignorant  and 
impractical  men  who  assume  the  role  of  experts,  never  having  run  an  engine 
a  day  in  their  lives. 

Every  diagram  which  is  presented  is  engraved  as  nearly  as  it  is  possible 
with  all  the  variations  which  the  original  contained,  in  other  words,  our  aim 
has  been  not  to  discriminate  in  favor  of  or  against  any  engine  builder's  work, 
but  to  produce  actual  fac-similes  in  size,  in  good  or  bad  points,  precisely  as 
the  originals  were  when  taken  from  the  engine.  The  full  intention  expressed 
with  reference  to  the  second  volume  has  not  been  realized.  The  only  point, 
however,  is  that  treating  upon  the  errors  of  different  motions,  which  is  in 
itself  an  exceedingly  wide  range  of  subjects,  and  requires  a  great  deal  of  prep- 
aration as  well  as  careful  experiment.  The  results  of  incorrect  motions  are 
shown  in  several  instances,  and  how  to  obtain  correct  diagrams  is  also  in  sev- 
eral instances  carefully  explained. 

As  referred  to  in  the  first  volume,  it  is  not  improbable  that  the  thkd 
volume  will  follow  the  second,  during  the  latter  part  of  1885,  in  which  a 
careful  analysis  of  motions,  the  result  of  errors  in  motion,  and  any  new 
features  with  reference  to  indicators,  or  possibly  with  reference  to  errors 
in  the  different  indicators  will  also  be  fully  illustrated.  Much  of  this  work 
has  now  been  done.  Careful  study  of  these  motions  has  been  made, 
experiments  are  completed,  but  Vol.  II  has  grown  so  rapidly,  by  including  in 
it  some  of  the  largest  marine  powers,  that  before  we  would  have  wished  it,  our 
printer  has  said  that  we  have  already  exceeded  the  limit,  and  the  book  is, 
therefore,  somewhat  larger  than  at  first  promised. 

The  aim  in  Vol.  II  has  been  to  meet  the  latest  practice  in  such  a  way 
that  the  wrorking  engineer  should  receive  from  it  practical  instruction,  and 
if  that  end  is  answered,  then  the  real  object  of  the  book  is  consummated. 


PREFACE.  ix 

Vol.  Ill  will  undoubtedly  follow  before  the  New  Year,  1886,  and  will 
illustrate  different  reducing  motions,  and  methods  of  giving  motion  to 
the  Indicator. 

The  labor  embodied  in  a  volume  of  this  kind,  and  especially  of  Vol.  II, 
cannot  be  estimated  by  any  one,  except  its  author.  It  has  cost  thousands 
of  miles  of  travel,  any  amount  of  personal  or  physical  inconvenience,  in  order 
to  obta  the  information  which  is  set  forth,  and  the  book,  as  presented, 
shows  the  latest  practice  in  American  high-pressure,  high-pressure  condens- 
ing and  compound  of  the  latest  steamers  launched  for  ocean  service,  as  well 
as  the  steam- jacketed  high-pressure  engines. 

The  tables  in  the  book  have  been  so  arranged  for  reference  as  to  embody 
some  new  principles,  and  the  table  of  areas  in  Vol.  I  having  been  found 
faulty,  that  in  Vol.  II  has  been  largely  computed,  and  any  errors  which  were 
found  were  corrected  before  its  being  issued. 

With  the  wish  that  the  book  may  answer  the  purpose  of  a  ready  and  re- 
liable reference  to  the  steam-power  owner,  or  others  interested,  especially 
those  men  in  charge,  we  send  it  on  its  way,  realizing  fully  that  it  contains 
some  faults,  and  without  doubt  many  omissions,  but  we  hope  also  that  it 
contains  much  which  is  valuable,  and  that  the  favor  with  which  Vol.  I  was 
received  may  be  extended  to  Vol.  II,  and  it  is  a  curious  fact,  up  to  the  time 
of  this  writing,  that  many  employers  have  ordered  Vol.  II  for  their  engineers, 
while  in  the  case  of  Vol.  I,  the  engineers  ordered  it  for  themselves.  Evi- 
dently the  employers  have  found  that  the  efforts  of  the  engineer  towards 
self-education  and  a  promotion,  were  for  their  interest,  and  we  welcome  this 
as  a  sign  of  encouragement,  especially  to  the  stationary  engineers,  to  con- 
tinue to  improve  themselves,  which,  we  know  they  are  doing,  in  many 
instances  when  they  can  ill-afford  the  expense.  "  Knowledge  is  power,"  and 
a  stationary  engineer  can  control  his  power  with  knowledge,  to  his  own 
benefit,  far  better  than  by  lack  of  knowledge,  as  so  many  have  already  found. 
The  author  will  be  thankful  to  any  of  the  readers  of  this  work,  who  will 
point  out  any  error  or  who  will  suggest  important  points  of  practical  use  to 
be  covered  in  Vol.  Ill, 

THOMAS   PEAY,  JR. 

NEW  YORK,  January  1,  1886. 


PREFACE  OF  1909. 


The  appliances  for  the  use  of  the  Indicator  have  multiplied  in  number,  but 
like  too  many  other  such  matters,  they  are  many  of  them  of  infinitely  small 
practical  use,  and  so  the  real  status  of  the  Indicator  is  little  changed  in  its 
useful  sense,  and  so  after  almost  looking  for  the  replacing  of  u  Twenty 
Years  "  ^72  th  some  later  book,  it  is  a  great  pleasure  to  the  author  to  write 
down  a  verification  of  the  good  judgment  of  the  owners  of  the  nearly  eighteen 
thousand  copies  which  have  found  their  way  to  the  engineers  in  all  of  the 
countries  of  the  earth  where  steam  power  is  used. 

In  the  year  1906,  up  to  October  4th,  on  which  this  little  addition  is  written 
for  the  printer,  over  eleven  hundred  copies  have  been  sent  out,  letters  from 
India,  Alaska,  New  Zealand,  Sandwich  Islands,  China,  Siberia,  Russia, 
Greece,  Egypt,  Persia,  Japan,  Mexico,  and  Brazil,  and  others  are  received; 
some  of  them  have  been  clients  for  years,  and  in  the  fleets  of  ships,  many  of 
the  owners  have  furnished  their  men  with  copies. 

The  real  progress  in  the  economy  of  using  steam  comes  only  from  a  correct 
use,  and  this  from  proper  knowledge,  and  this  broadens  more  and  more  each 
year. 

This  is  all  the  more  true  for  the  simple  reason  that  the  action  of  steam 
under  pressure  varies  but  very  little,  so  far  as  our  knowledge  of  it  goes ;  men 
have  made  seemingly  different  applications,  to  engines,  turbines,  and  other 
methods,  but  the  action  of  steam  is  just  as  it  was  when  Regnault  and  Rankine 
worked  out  so  much  of  the  facts  as  made  it  easy  for  the  man  who  "  reads  as 
he  runs"  to  apply  with  the  utmost  attainable  economy. 

It  is  always  a  pleasure  to  receive  letters  telling  of  troubles  and  how 
they  were  overcome.  Much  that  is  valuable,  and  which  in  another  book 
will  be  very  interesting,  has  in  this  way  come  to  hand ;  it  is  being  put  into 
shape,  and  it  will  as  it  now  looks,  reach  the  printer  later  on,  for  new  readers. 

The  gas  engine  has  in  some  ways  proved  unable  to  make  a  "  revolution" 
as  was  expected,  and  to  replace  steam ;  there  are  many  places  where  its  use 
has  succeeded,  but  it  has  like  the  turbine,  been  found  wanting  in  the  broad 
application  that  steam  fully  and  successfully  covers,  completely. 

Thanking  each  and  all  for  their  courtesy  and  approbation,  and  wishing  for 
each  the  full  measure  of  personal  success  and  reward,  and  that  it  may  long 
continue,  and  we  may  all  become  more  and  more  competent  to  deal  with  the 
problems  to  which  many  have  given  the  largest  number  of  the  years  of  our 
lives,  I  send  this  edition  on  its  way  with  only  kindly  wishes  to  all  and  every 
one  of  its  readers.  THOMAS  PRAY,  JR. 

All  Interests  in  the  Publication  and  Copyrights  have  been  legally  transferred  tg 
the  American  Steam  Gauge  and  Valve  Mfg.  Co.,  September,  1908. 


INDEX. 


FAOl 

Introduction 1-4 

The  Thompson  Indicator ;  How  to  Attach  it ;  What  to  Use     ...       4 
How  to  Adjust  the  Tension  of  the  Paper  Barrel  Spring  ....       4 

Applying  the  Pencil  to  the  Paper ;  How  to  do  it  Right   .         .         .         .  4,  5 

Getting  the  Diagram  in  the  Center  of  the  Paper  ;  Things  to  Avoid          .       5 
How  and  Where  to  Attach  the  Indicator  .......       5 

Clearance  or  Clear-way  ;  Size  of  Pipe  ;  Be  Sure  of  a  Clear  Hole      .         .       5 
Side-pipe  and  Three-way  Cock  Worthless         ......       6 

Reasons  Why  ;  Some  Facts  in  Connection  ;  Avoid  Elbows  and  Valves  ; 

Caution      ............       6 

How  to  Make  the  Pencil  Lead  do  Good  Work ;  How  to  Sharpen  .  .  7 
Blowing  out  Connection  Pipes  ;  Adjusting  the  Indicator  Pipes  ;  Oil  to 
be  Used ;  Balance  the  Paper  Cylinder ;  Do  not  Work  with  Dirty 
Hands ;  How  the  Paper  Should  Fit ;  Heating  the  Instrument ; 
Caution  About  Taking  the  Atmospheric  Line,  and  Why  ;  Take  the 
Diagram  First,  Atmospheric  Line  Afterwards  ;  Caution  About  Shut- 
ting the  Cock  Closely  ;  Making  Record  of  Data  at  the  Time  of 

Taking 7 

The  Steam  which  the  Spring  Will  Take 8 

A  Suggestion  ;  Washers  for  the  Indicator  Piston  ;  Things  to  Look  Out 
for  so  as  to  Avoid  Trouble;  The  Kind  of  Oil,  and  Why;  Which 
Spring  to  Use ;  Why  the  Small  Diagrams  are  Not  Correct        .         .       8 
Changing  the  Spring ;  How  to  do  it  Correctly        .         .         .         .         .9 
Hints  in  Connection  with  Changing ;  General  Hints         ....       9 
The  Thompson  Improved  Indicator  with  Detent  Motion  .         .         .         .10 

Swivel  Pulley  for  Conveying  the  Motion 10 

Methods  of  Attaching  the  Indicator  or  Making  the  Reducing  Motion      .     11 
Some  Faults  of  the  Pendulum  Motion ;  Cautions  in  its  Use  ;  How  to 

Get  the  Best  Motion  from  a  Pendulum     ......     11 

Bacon's  Attachments  for  Pendulum  or  Pantograph;  How  to  Use  Them  12, 13 
How  to  Set  the  Pantograph  Motion .         .         .         .         .         .         .         .13 

Working  by  Right  Angles ;  Caution         .......     13 

Pantograph  on  Horizontal  Cross-head       .  .         .         .  .14 

Pantograph  and  How  to  Apply  it  Accurately   .         .         .  14, 15 

Sliding  Loop;  A  New  Thing          .  -,         .         .         .         .         .        ,         .     15 

Computing  the  Indicator  Diagram    .         .  .        ....     16 

Different  Methods  ;  Caution  as  to  the  Correctness  of  Data  ;  Working  up 
the  Diagram  ;  The  Unit  of  Horse-power  ;  The  Process  of  Comput- 
ing ;  Obsolete  Methods  Mentioned    .         .         .         .         .         .         .     16 

Polar  Planimeter  .         .17 


in  INDEX. 

PASS 

The  Process  of  the  Computation  of  the  Diagram  by  Means  of  the  Plan- 

imeter  Explained ;  How  to  Use  the  Planimeter  Correctly        .         17,  18 
Measuring  Diagrams  with  Loops ;  Negative  Quantities          .         .  19 

Ascertaining  the  Power  from  the  Planimeter  Reading ;    How  to  Reduce 
Area  to  Mean  Pressure ;  The  Mean  Pressure  to  Horse-Power ;  An 
Instance ;  How  to  Test  the  Planimeter  for  Correctness          .        .       20 
Different  Factors  in  the  Diagram  .        .-       .        .        .        .        .       20 

Necessity  of  Reliable  Data    .        .        ....        .        .        .        .       21 

Lesson  I .         22-26 

Bacon's  Method  of  the  Theoretical  Carve  by  Ordinates,  with  an  Analysis  of  the  Various  Lines 
of  the  Instrument. 

Lesson  H .        .        26-30 

The  Theoretical  Curve  Applied  to  a  Corliss  Engine— The  Same  Application  Made  to  a  Steam- 
ship Engine,  with  Directions  to  the  Student  as  to  all  the  various  Lines  and  Terms. 

Lesson  in V.        .        .        .         30-33 

Typical  Diagrams. 

Lesson  IV .  33-35 

A  Wheelock  Engine— The  Practical  Application  of  the  Indicator— An  Engineer  who  didn't 
Believe  in  the  Indicator— How  this  Diagram  was  Corrected— Waste. 

Lesson  V  .  ........          35-38 

Two  Interesting  Subjects— Locomotive  Practice  on  a  Stationary  Engine— Tardy  Admission- 
Steam  Wire  Drawn— A  Two  Hundred  Horse  Engine  Doing  Three  Hundred  and  Eighty 
Horse-Power—Lack  of  Economy. 

Lesson  VI 38-40 

A  High  Speed  Engine  with  Several  Kinks. 

jLesson  VII      .        .        .        .        .  .        .        .        .         40-46 

Harris-Corliss  Engine— An  Engineer  Learning  the  Practical— Lack  of  Reliance  Upon  the 
Three- Way  Cock  System  of  Taking  Diagrams— Curious  Diagrams— Fluctuations  of  the 
Regulator,  and  the  Reason  For  It— The  Actual  and  the  Mean— Both  Ends  Should  Do  the 
Same  Amount  of  Work— The  Rollins  Engine  with  Very  Light  and  Very  Heavy  Load- 
Something  About  Compression. 

Lessons  VIII-IX  4&-49 

Simultaneous  Diagrams— Their  Value  in  Adjustment  and  Indicating— Corliss  Engine  by  a 
Man  who  Used  Indicators— The  Amount  of  Theoretical  Utilized— Two  and  Two- 
Thirds  Pounds  of  Coal  per  Hour. 

Lesson  X ....        -         50-52 

Buckeye  Engine— Loss  of  Boiler  Pressure— Back  Pressure— Loops. 

Lesson  XI       .        .       ....       .        -,.•.-•: 52-55 

Corliss  Engine  Built  for  the  City  of  Boston— Pump— High  Pressure  and  Low  Pressure 
Diagrams— Coal  per  Horse-Power—Boiler  Pressure  Utilized— Its  Performance  After 
Put  at  Work  for  the  City  of  Providence. 

Lesson  XII     ..        .         .        ., 55-58 

The  Corliss  Pawtucket  Pumping  Engine— High  and  Low  Pressure  Diagrams— Dimensions- 
Duty. 

Lesson  Xin  .        .        .        .         .        .        .        .      ;.        .         58-61 

Corliss  Engine— A  Curious  Fault  Found  by  the  Indicator— Indicator  at  Fault— Another 
Curious  Case— StiU  Another— Trouble  in  the  Indicator— Trouble  in  the  Indicator 
Cylinder. 

Lesson  XIV .         61-63 

A  Brown  Engine  in  Bad  Condition— Queer  Looking  Diagram— Misuse  of  Steam— Setting  an 
Engine  by  Marks  or  by  the  Indicator— Indicator  out  of  Order. 

Lesson  XV      .  .        .        .        •.        .        .         63-66 

Harris-Corliss  Engine— Another  Case  of  Setting  Valves  by  Marks— A  Disgusted  Engineer- 
Queer  Diagrams— The  Indicator  and  its  Results. 


INDEX.  xiii 

MOB 

Lesson  XVI  ....  66-69 

Buckeye  Engine— One  Indicator  and  a  Three-Way  Cook— Deficiency  in  Realized  Boiler 
Pressure— A  Contrast— Harris-Corliss  Engine— Realization  of  Boiler  Pressure— Indi- 
cator Attached  by  Three-Way  Cock. 

Lesson  XVII  .......  .  69-71 

Greene  Engine— Queer  Practice— Loops  and  Late  Steam— A  Curiosity. 

Lesson  XVIH         ....  .  71-75 

Saw-Mill  Diagram— Large  Back  Pressure— Lack  of  Economy— Radically  Bad  Diagrams- 
Curious  Figures— Something  to  Study— Two  of  the  Worst  Possible  Misuses  of  Steam. 

Lesson  XIX  ,  75-80 

The  Results  of  a  Visit— How  Some  Men  Run  Corliss  Engines— A  Hard  Working  Engine- 
Lesson  in  Natural  History— What  an  Hour's  Work  Did— $12  a  Day  Saved— How  the 
Valves  Were  Changed  to  Accomplish  the  Result— Careful  Analysis  of  all  the  Changes- 
Two  Thousand  a  Year. 

Lesson  XX 80-82 

The  Hyperbolic  Curve— A  Simple  and  Correct  Way  of  Laying  it  Out,  with  Full  Instructions 
How  to  Do  It. 

Lesson  XXI  .  82-84 

Another  Method  of  Laying  Out  the  Hyperbolic  Curve,  with  Full  Directions  How  to  Do  It— 
The  Rollins  Engine— Elegant  Card. 

Lesson  XXII  .  84-87 

An  Experiment— Late  Lines— Mai- Ad  justment  of  Valves— Peculiarities  of  Practice— Small 
Pipes— Bad  Work. 

Lesson  XXIII         .         .  87-89 

An  Expensive  Engine  to  Run— A  Bad  Diagram— An  Instructive  Lesson— Lack  of  Vacuum 
and  Boiler  Pressure— Insufficient  Steam  Passages— Wire-Drawn  Steam— A  Wright 
Engine  Thirteen  Years  Old— A  Comparison. 

Lesson  XXIV 90-92 

Corliss  Engine  Thirty  Years  Old— An  Economical  Result— An  English  Engine  in  Comparison 
—Some  Interesting  Features. 

Lesson  XXV  ....  ...  92-94 

A  Search  After  Information— What  Occurred— Queer  Looking  Diagrams— Late  All  Round- 
Bad  Practice — A  Radical  Improvement. 

Lesson  XXVI 94-100 

The  Planimeter  Applied  to  the  Computation  of  Indicator  Diagrams,  with  Full  and  Explicit 
Directions  What  to  Do,  What  Not  to  Do,  and  How  to  Do  It— Which  Way  to  Run  the 
Flanimeter — Where  to  Commence — How  to  Prove  Your  Reading — How  to  Measure 
Loops  or  Expansion  Below  the  Atmospheric  Line,  and  Much  Other  Valuable  Informa- 
tion with  Regard  to  the  Use  of  this  Instrument. 

See  also  pp.  17  to  20. 
Lesson  XXVII 100-102 

An  Old  Style  Corliss  Engine— One  That  Had  Been  Abused— What  an  Intelligent  Engineer 
Accomplished— A  Contrast— Old-Fashioned  Slide  Valve  Wire  Drawn. 

Lesson  XXVIII       .  .  .     103-105 

One  of  the  Most  Important  Lessons  for  Beginners— What  Will  Sometimes  Happen  in  Actual 
Practice— How  a  Man  Discovered  His  Own  Unreliability— Some  Curious  Looking  Marks 
on  a  Diagram— What  Not  To  Do. 

Lesson  XXIX .  106-109 

Curiosities  of  Steam  Practice— Thick-Headed  Steam  Users— Heating  by  Back  Pressure  Car- 
ried to  Excess. 

Lesson  XXX .     109^111 

The  Hartford  Engineering  Company's  Engine— Good  Steam  Lines— The  Reynolds-Corliss 
Engine— A  Contrast  in  Engineering  Experience. 

Lesson  XXXI ...      111-114 

Indicating  an  Engine  by  Telegraph— A  Positive  Fact— Queer  Looking  Lines— The  Results  of 
a  Careful  Examination— Tool  Chest  in  a  Steam  Chest— The  Result  of  Careful  and 
Searching  Investigation— A  Converted  Engineer— Practical  Jokes  and  a  Curious  Finale. 


xiv  INDEX. 

PAGE 

LessoD  XXXII      ,~.        .        .        .        ....         .        .     115-118 

An  Engineer  Without  an  Indicator— A  Harris-Corliss  Engine  in  Bad  Condition— Ignorance 
and  Avarice— What  a  Few  Hours'  Work  Accomplished— And  What  a  Saving  was  Made 
by  an  Adjustment  of  the  Valves. 

Lesson  XXXHI .        .     119, 120 

Reynolds-Corliss  Running  by  High  Pressure  and  a  Sensible  Engineer. 

Lesson  XXXIV      .        .        .        .      ...        .        ....      120-123 

The  Misuse  of  Steam,  or  Natural  History  by  the  Indicator— Something  For  Beginners  to 
Study  Closely— How  to  Make  the  Corrections  to  Accomplish  Readjustment. 

Lesson  XXXV        .        . .     123, 125 

Curiosity  in  Steam  Practice  from  an  English  Engineer— High  Water  Consumption— Very 
Peculiar  Diagrams— One  End  of  an  Engine  Doing  More  Than  All  the  Work— One 
Engine  of  a  Pair  Stopped,  and  Less  Fuel  Used. 

Lesson  XXXVI       .  ........      126, 127 

Wheelock  Engine  Doing  All  the  Work  on  One  End— Peculiarly  Poor  Diagrams— A  Lesson 
for  Study. 

Lesson  XXXVII .        .      128-130 

A  High  Speed  Engine  With  Peculiar  Results— The  Difference  Between  Boiler  Pressure  and 
Realized  Pressure,  and  the  Percentage  as  Between  Two  Ways  of  Working  Steam— An 
Interesting  Study. 

Lesson  XXXVIII .        .      130-132 

A  Brown  Engine— A  Very  Fine  Diagram— An  Interesting  Subject. 

Lesson  XXXIX 132-134 

The  Difference  Between  Representation  and  Actual  Performance— A  Corliss  Engine  Put  to 
the  Theoretical  Test. 

Lesson  XL 135-137 

The  Latest  Departure  in  High  Speed,  the  Armington  &  Sims  Engine— A  Very  Interesting 
Subject— An  Experiment  with  Very  Gratifying  Results— Something  for  Engineers  or 
Beginners  to  Study— Close  of  the  Practical  Lessons. 

Lesson  XLI 138-143 

Demonstrating  the  Actual  Point  of  Cut-off  from  Steam  Used  when  the  Lines  are  Indistinct 
and  the  Terminal  Pressure  Not  Made  Use  of— Reasons  for  Discarding  Old  Theories- 
Example  Diagram  from  Leaky  Valves— Proof  of  its  Correctness— Full  Directions  for 
Making  the  Demonstration. 

Lesson  XLII 143-146 

Demonstration  of  the  Point  of  Cut-off  and  How  to  Lay  Out  the  Theoretical  Curve— Full  Ex- 
planations for  the  Combination  of  these  Two  Distinct  Propositions. 

Lesson  XLIII 146, 147 

Application  of  the  Previous  Demonstration  to  a  Sound  Steamer. 

Lesson  XLIV          .         .         .         .        .         .        .         .         .        .      148-152 

A  Modern  Steamship  Engine  Examined  for  the  Determination  of  Several  Points,  among 
which  are  Two  Different  Indicators-  Interesting  Result— How  Compound  Engines 
Work. 

Lesson  XLV  ...         .         .         .         .         .         .         .      152-154 

A  Badly  Throttled  Engine,  Great  Loss  in  Boiler  Pressure  and  in  Valves. 

Lesson  XLVI          ...        ."'"..'.        .         .        .        .         .      154-156 

High  Speed  Diagram— Trial  of  the  Indicator— What  Makes  Fluctuations  in  the  Cylinder. 

Lesson  XLVH        .         .         .         .         .         .         .         .         .         .      156-158 

Medium  High  Speed  Engine,  Large  Load— Application  of  the  Demonstration— Clearance 
Unimportant. 

Lesson  XL VIII      ....  .        .     159-161 

An  Expensive  Use  of  Steam— Actual  Fact  and  Possibility— Comparison  Which  Shows  What 
Might  Be  if  the  Mechanical  Construction  was  Right. 

Lesson  XLIX ,  .  161-165 

A  High  Speed  Engine  Speeded  Up  to  Try  the  Thompson  Improved  Indicator,  435  a  Minute— 
The  Application  of  Both  Demonstrations  and  the  Clearance  Added— What  Makes  the 
Wavy  Line  of  Expansion— Exhausting  33  Pounds  Above  the  Atmosphere. 


INDEX.  xv 

PAGE 

Lesson  L 165-167 

Carrying  Steam  Full  Stroke  and  Exhausting  Under  Excessive  Back  Pressure— Lack  of 
Realized  Pressure— Late  Admission— A  Comparison  for  Results. 

Lesson  LI 167,168 

Harris-Corliss  Engine— Diagram  Distorted  by  Incorrect  Motion. 

Lesson  LIT 168-170 

A  Curiosity  in  Diagrams. 

Lesson  LIII 170,171 

Adjusting  Corliss  Engine  Valves,  the  Changes  Made  and  the  Reason  Why  Illustrated. 

Lesson  LIV  172-174 

Expensive  Cut-off  by  Cheap  Attachments. 

Lesson  LV      .  .  .  ....      174-176 

Corliss  Compound,  High  Duty  Pumping  Engine— The  Highest  Realized  Efficiency— Cost  of 
Running  from  Official  Figures— Duty  and  Some  Other  Interesting  Facts. 

Lesson  LVI    ....  .  ...      177-179 

Short  Connections  on  an  Engine  Which  Had  Been  Adjusted  for  a  Three-way  Cock  and  Side- 
pipe— Contrast— Excessive  Compression. 

Lesson  LVII ...      179,180 

Three-way  Cock  and  Side-Pipe  on  Same  Engine  as  the  Preceding  Lesson — Compare  the 
Two  Sets  of  Diagrams. 

Lesson  LVIII '.         .         .      181-183 

High  Cost,  Low  Economy  Steam  Yacht— Compound— Peculiar  Diagrams— Low  Efficiency. 

Lesson  LIX 183-186 

An  Ocean  Steamship  Compound— Peculiar  Diagrams  and  Curious  Results— Lack  of 
Efficiency. 

Lesson  LX .  186, 187 

An  Experiment  by  an  Engine  Builder— A  Poor  Imitation  of  a  Good  Engine. 

Lesson  LXI    ....  ....      188-190 

Difference  of  Realized  Pressure  in  the  Cylinder  at  Different  Speeds— A  Lesson  on  Feed- 
pipes. 

Lesson  LXII .        .190,191 

Another  Lesson  on  Feed-pipes— A  High-speed  Engine  in  Comparison  with  Previous 
Lessons. 

Lesson  LXIII  .        .        .         .        ,        .  -     .        .        .      192,193 

Sound  Steamer  with  Large  Cylinder  as  Compared  with  Previous  Marine  Engines. 

Lesson  LXIV 193-195 

Large  Low-pressure  Engine  on  Sound  Steamer— 4,500  H.  P.  in  a  Single  Cylinder. 

Lesson  LXV 196,197 

An  Overloaded  Engine,  46  Pounds  Terminal  Above  the  Atmosphere. 

Lesson  LXVI          .  .  ...      197, 198 

Harris-Corliss  Engine  Doing  Double  Work. 

Lesson  LXVII        ....  .  .  198-202 

The  Latest  Triple  Compound  Ocean  Steamship  Engine— Something  to  Study— A  13,000  H.  P. 
Machine— Somewhat  Curious  Results— Some  Lessons— Lack  in  Realized  Pressure  as 
well  as  of  Yalves  Handling  the  Steam. 

Lesson  LXVIII      ...  ....      202-205 

German  Built  Corliss  Compound,  but  Without  the  Corliss  Valve-gear. 

Lesson  LXIX 205,  206 

Mistake  in  Indicator  Motion  and  Curious  Result— How  to  Use  the  Planimeter  on  Such  a 
Diagram. 

Lesson  LXX 207-SU 

Defects  Shown  by  the  Indicator— Comparisons— A  New  Engine  Leaking  Badly— How  This 
Occurred  and  the  Reasons— An  Experiment  by  a  Builder— Lack  in  Realized  Pressure, 
no  Expansion,  Trouble  in  the  Exhaust— Corliss  Steam  Jacketed  Showing  a  Strange 
Contrast  to  the  Other  Diagrams  in  the  Same  Lesson. 


xvi  INDEX. 

PAGK 

Lesson  LXXI ....  211-217 

An  Experiment  with  Different  Indicators  on  the  Same  End  of  the  Same  Cylinder,  at  the 
Same  Time— Very  Curious  Looking  Cards— Queer  Expansion  Lines— Change  of  Pres- 
sure, Volume,  Temperature— Friction  and  Loaded  Cards  Together— Something  About 
the  Change  of  Speed  in  the  Crank— Engine  Running  276. 

Lesson  LXXII 217-221 

Extreme  High  Speed,  500  to  640  Revolutions— The  Thompson  No.  2  Indicator,  or  Small 
Paper  Cylinder— Diagrams  at  536  Revolutions  per  Minute— 562  Revolutions— Queer 
Expansion  Lines  and  Queerer  Compression — Difference  Between  Different  Indicators 
at  the  Same  Instant— 562  Revolutions— 642  Revolutions— Where  the  Indicators 
Stopped  to  Rest— Deductions. 

Lesson  LXXIII 221-224 

American  Compound  on  River  Steamer— Lack  in  Realized  Pressure— Falling  df  in  the 
Compound  Cylinder— Curious  Expansion  Line,  Badly  Wire-drawn— Lack  of  Realiza- 
tion in  Volume— A  Most  Interesting  Lesson— What  Could  be  Done  if  the  Pressure  in 
Both  Cylinders  Were  Utilized— A  Wide  Difference  Between  Actual  and  Theoretical. 

Lesson  LXXVI .  225-227 

A  Compound  Non-Condensing,  or  Compound  Hish  Pressure  Engine— Very  Curious  Dia- 
grams—An Erratic  Governor— Lack  of  Realized  Pressure— An  Attempt  to  Run  the 
Compound  Cylinder  High  Pressure,  a  Curious  Result— The  Compound  Cylinder 
Working  as  designed— Very  Erratic  Diagram— Eight  Pounds  of  Fuel  per  Horse-Power 
an  Hour. 

Lesson  LXXV 227,  228 

Fishkill  Landing  Corliss  Engine— A  Diagram  Taken  from  Every-day  Work  to  Ascertain 
What  Was  Being  Done— Handsome  Lines— No  Necessity  for  Clearance  When  Work- 
ing for  Expansion. 

Lesson  LXXVI .         .         229-232 

An  Ocean  Steamship  Compound  Fitted  with  Corliss  Valves. 

Lesson  LXXVII 232-235 

An  Ocean  Steamship  Compound — A  Considerable  Difference  Caused  by  Unequal  Side-pipe 
Attachments. 

Lesson  LXXVIH  .         .         .   .      .         .         .         .         .         235,  236 

Condensing  Beyond  Economy. 

Lesson  LXXIX 237,238 

An  Old  Corliss  Engine— Its  Economy— Cost  of  Horse-Power  per  Hour— Authentic  Data. 

Lesson  LXXX 239-241 

An  Overloaded  Corliss  Engine— Defects  of  General  Arrangement  in  Feed-pipe— Difference 
in  the  Ends  in  Amount  of  Work— Necessity  of  Simultaneous  Diagrams  for  Adjustment 
or  Power— An  Interesting  Lesson. 

Lesson  LXXXI .         241-244 

An  Ocean  Compound— Some  Curious  Results. 

Lesson  LXXXII  .         .         V        .         •   .      •         •         •         •-        244-24S 

Defective  Construction— An  Engine  Which  Leaked,  Raced,  Piston  Covered  the  Indicator 
Hole— A  Combination  of  Defects— An  Incident  in  the  Use  of  the  Pantograph— A 
Curious  Expansion  Line— A  Curiosity— Experimental  Steam  Engine  Building. 

Lesson  LXXXIII 249-258 

For  the  Beginners— What  an  Indicator  is  For— The  Ideal  or  Perfect  Diagram— Difference  of 
Release  and  Compression— Excessive  Steam  Lead,  or  Compression— General  Defects 
Which  Are  to  be  Looked  For— Circumstances  Which  Influence  the  Different  Lines- 
Change  of  Release  and  Compression— Cushion,  What  it  Accomplishes— Variations 
from  the  Ideal  Diagram— Some  Examples  and  What  Caused  Them— Wire-drawing— 
Late  Release- Imperfect  Vacuum— Throttling  -Quickening  the  Time  of  Valves— Late 
Admission— Rolling  the  Eccentric  Forward— Obtaining  Both  Points  by  One  Movement 
—How  to  Adjust  These  Matters  on  Different  Engines— Prick-Punch  Marks,  Cold 
Chisel  Slashes  not  to  be  Noticed  or  Relied  on— Steam  Chest  Diagrams,  What  They 
Are  For,  Their  Importance  and  Value— Other  Places  to  Attach  the  Indicator- Caution 
as  to  Condensing  Engine  Attachments— Suggestions— The  Diameter  of  a  Piston-rod 
Out  of  the  Crank  End  of  the  Engine. 

Lesson  LXXXIV  .  .       ;.         ...         .          .         259, 26(] 

Water  per  Horse-Power  from  the  Diagram,  or  Steam  Consumed -Full  Directions  for  the 
Computation. 


INDEX. 


xvii 


PAGK 

Another  Method  of  Computing  the  Water  per  Horse-Power  per  Hour     .  261 

Vacuum 261, 262 

Temperature  of   the  Vacuum  at  Different  "Pounds  per  Square  Inch" 

and  "  Inches  of  Mercury."          ........  261 

Total  Heat        ...        .        .        .         .         .         .         .         .         .261 

Inches  of  Mercury,  Expansion  of  Mercury         ......  262 

The  Density  of  Steam       .         . 262 

Temperature  of  Vacuum   .  .         .         .         .         .         .         .   262,263 

An  Improved  Draft  Gauge  for  Chimneys. 264-268 

How  to  Test  Feed-water  for  Boilers — Testing  Feed-water  Heater — Test- 
ing Thermometers      ..........  269 

Lusterless  Finish  on  Tempered  Steel .  271 

Patent  Varnish          .... 271 

Calorimeter  Test 272 

Iron  Paint          .         .         .         .         .'       .         .         .         .         ..        .         .  273 

Joule's  Equivalent     .         ...         .         . 273 

Coloring  Soft  Solder  Yellow 274 

Recipes  for  Soldering  Fluid -7        .         .         .  275 

SAFETY-VALVE  PROBLEMS — To  Find  the  Pressure  of  the  Ball  as  it  Hangs    .  275 
To  Obtain  a  Certain  Pressure  with  the  Ball      .         .         .         .         .         .  275 

To  Obtain  a  Ball  for  a  Certain  Pressure   . 276 

To  Ascertain  the  Proper  Size  of  the  Safety  Valve  for  Any  Given  Grate 

Surface       ....-.." 276 

Restoring  Tarnished  Gold .  276 

Water  in  the  Cylinder       . 277 

To  Cut  Gauge  Glasses  to  Any  Length 277 

Babbitt  Metal,  Different  Formulae     .      ' .  .         .   '     .         .         .         .         .278 

Useful  Numbers  for  Rapid  Approximation  ^ ....  279 

The  Properties  of  Saturated  Steam  .         .        ...        .        .        .         .  280 

Table  I.— Properties  of  Saturated  Steam,  1  to  200  Ibs.     .        .        .        .281 

"     II.— Areas  of  Circles  from  J"  to  90"  Diameter        .         .        .         .282 

"     III.— Hyperbolic  Logarithms .  283 

'-'     IV.— Effect  of  Expansion  with  Equal  Volumes  of  Steam         .         .  283 
w     V,— Fractions  of  an  Inch  in  Decimals      .  284 


YEARS  WITH  THE  INDICATOR. 

College,  New  Haven)  came  into  our  hands,  that  we  commenced,  in  the  latter 
part  of  1865,  to  adjust  the  valves  of  steam  engines  by  the  use  of  the 
indicator.  If  we  had  only  been  as  careful  then  in  keeping  our  memoranda  as 
we  are  to-day,  we  could  produce  some  facts  with  reference  to  some  of  the  best 
steam  engine  builders  in  the  country  that  would  open  the  eyes  of  our  readers 
wide  with  astonishment.  In  fact,  it  is  a  matter  that  is  known  to  some  people 
still  living  that  we  had  a  long,  almost  hand-to-hand  fight.  The  indicator  was 
denounced,  and  the  man  who  had  the  presumption  to  attempt  to  get  away 
from  the  old  prick-punch  marks  and  cold  chisel  dents  on  main  shaft, 
eccentrics,  straps,  valves  and  connections,  was  denounced  as  strongly  as  the 
English  language  was  capable  of.  In  fact,  invectives  were  freely  used ;  but 
all  that  has  passed  away  and  much  credit  is  due  to  Mr.  Charles  B.  Richards 
for  his  having  studied  the  defects  of  the  old  indicator,  and  by  the  use  of  the 
Richards  indicator  eliminated  many  of  these  defects  of  the  steam  engine 
builders,  until  finally  the  very  men,  who  in  1865  were  extremely  vindictive, 
because  their  old  ways  of  working  had  been  declared  incorrect,  are  now  the 
men  who  make  free  use  of  the  indicator  and  who  advocate  it  and  advise  it. 

This  change  has  been  brought  about  within  the  twenty  years  covered  by 
our  own  practice,  terminating  with  the  issue  of  this  Volume  II.  But  the 
indicator  is  now  of  use  for  more  purposes  than  one.  In  1880  we  commenced 
a  series  of  articles  in  a  paper  then  edited  by  us,  which  shortly  after  grew  into 
a  large  circulation,  and  which  has  done  much  to  awaken  working  engineers 
to  the  fact  that  by  extending  their  knowledge  they  could  make  themselves 
more  valuable  and  could  produce  higher  economy  for  their  employers.  These 
men,  many  of  them,  have  not  been  slow  to  avail  themselves  of  this  knowledge, 
and  in  very  many  cases  they  have  been  personally  benefited  by  being  promoted 
to  better  positions,  and  there  are,  no  doubt,  many  others  who  will  be  rewarded 
in  the  same  way ;  but  it  is  a  work  of  time.  Employers,  on  the  other  hand,  have 
been  slow,  in  some  cases,  to  recognize  the  value  of  the  indicator  and  its 
application,  and  particularly  the  fact  that  the  engineer  who  was  familiar  with 
it,  was  worth  more  money  to  him  or  them  than  one  who  was  ignorant  of  it. 
Like  all  other  innovations  on  ancient  practice,  the  working  engineer  must  be 
patient  and  must  produce  the  results,  and  then  no  man  or  class  of  men  are 
quicker  than  employers  to  find  the  benefit  of  the  change  accruing  from  the 
proper  application  of  the  indicator ;  then  the  men  who  can  handle  it  with 
best  purpose  can  certainly  receive  all  that  belongs  to  them.  But  during  the 
years  past  employers  have  a  great  many  times  been  seriously  misled  by  men 
who  adopted  the  word  "expert"  as  a  prefix  or  suffix,  and  who  are  really 
incompetent,  and  they  have  paid  dearly  for  this  experience,  so  that  really  the 
indicator  and  its  advocates  must  be  prepared  to  outlive  this  reputation, 
which  is  no  fault  of  the  indicator,  but  rather  of  a  class  of  men  who  live  upon 
the  credence  of  others.  But  taking  it  all  in  all,  the  use  of  the  indicator  has 
vastly  extended  within  the  last  four  or  five  years. 

Following  up  the  improvements  which  have  been  made  in  the  steam 
engine  indicator  since  the  author's  first  connection  with  it  (and  during  which 
time  he  has  owned  almost  every  indicator  which  has  been  manufactured,  to 


TWENTY  YEARS  WITH  THE  INDICATOR.  3 

any  extent  at  least,  and  some  which  never  should  have  been  manufactured  and 
are  not  now),  and  finally  found  the  instrument  which  for  all  purposes  has 
given  the  most  reliable  results,  including  all  that  is  expected  of  an  indica- 
tor, and  that  is,  the  Thompson  Improved  Indicator,  which  is  the  only  one 
illustrated  in  this  volume,  and  which  the  author  uses  exclusively  in  his  own 
practice  on  trials  for  power,  on  tests  for  the  position  of  the  valves,  for  the 
correctness  of  working  steam  and  for  all  purposes  wherever  he  is  profession- 
ally called  to  attend  to  adjustment,  correction,  economy,  or  power  tests ;  and 
in  connection  with  this  indicator  he  has  used  everything  which  has  been 
found  in  the  market,  ancient  and  modern,  up  to  the  issuing  of  this  book, 
making  trials  of  different  speeds,  under  different  conditions,  with  different 
pressures,  and  with  different  positions  of  valves,  and  the  trial  has  in  every 
case  re-asserted  the  correctness  of  his  adoption  of  the  Thompson  Improved, 
and  in  some  cases  where  very  serious  errors  were  found  in  either  one  or  the 
other  essential  requirement  or  relation  of  valve,  valve  action,  working  of 
steam,  or  large  variation  in  the  amount  of  power,  under  identically  the  same 
circumstances.  The  author  desires  to  state  here  that  he  has  no  connection 
with  any  indicator  attachment,  engine  or  steam  appliance,  no  interest  financi- 
ally, direct  or  remote  ;  and  wherever  comparisons  are  used  they  are  used  as 
matters  of  fact  for  the  information  of  the  reader  and  with  the  intention  that 
such  information  shall  be  reliable,  our  sole  interest  being  to  make  this  book 
more  valuable  than  any  that  has  preceded  it. 

The  various  defects  which  are  found  in  the  old  indicators  have  gradually 
been  removed;  some  of  them  have  been  faults  of  mechanism,  others  of 
mechanical  construction,  while  others  have  led  to  a  change  in  mechanism  and 
construction,  and  in  some  cases  in  the  proportion  of  parts  and  to  a  decided 
change  in  the  mechanism  adopted  to  produce  the  required  result.  The 
lessons  which  follow  this  are  very  largely  from  our  own  practice.  Some 
curious  examples  are  shown,  and  in  every  case  diagrams  are  engraved  pre- 
cisely as  they  were  taken,  full  size,  and  can  form  the  basis  of  comparison  or 
can  be  figured  from,  without  any  reduction  of  proportion  or  percentages.  It 
is  proposed  to  introduce  everything  up  to  the  most  recent  practice,  particu- 
larly that  of  some  steamships,  the  diagrams  of  which  have  never  been  printed 
before.  Many  of  the  matters  introduced  are  original,  particularly  that  of 
demonstrating  the  cut-off  from  the  actual  pressure  of  steam  from  some  point 
on  the  expansion  line.  Some  of  the  methods  of  working  out  diagrams  we 
have  never  seen  in  print  before,  and  some  of  the  oldest  engineers  and  best 
scientific  men  in  the  country  have  carefully  gone  through  the  demonstrations 
and  pronounced  them  mathematically  correct.  All  these  demonstrations  are 
put  in  plain  language,  without  mathematical  or  algebraic  formula,  so  that 
everyone  can  fully  understand  and  work  from  them  without  reference  to  any 
of  the  works  upon  higher  mathematics.  Volume  II.  is  intended  to  cover  the 
whole  ground,  and  there  is  no  reference  from  Volume  II.  to  its  predecessor, 
and  no  need  of  reference  from  one  to  the  other  for  any  purpose  of  computa- 
tion. Volume  II.  will  be  found  to  contain  a  far  broader  scope  than  Volume 
I.,  and  it  is  intended  to  be  a  companion  to  the  working  engineer,  to  answer 


4  TWENTY  YEARS  WITH  THE  INDICATOR. 

his  questions  at  all  times,  and  to  answer  them  in  such  a  way  that  whatever 
may  be  the  situation  or  position,  he  can  at  once  adapt  himself  and  his  indicator 
fco  the  case,  with  a  certainty  of  correct  results. 


THE  THOMPSON  INDICATOR.— HOW  TO  ATTACH  IT,  AND  WHAT  TO  USE. 

Figs.  A  and  B  represent  respectively,  A  an  outside  view  and  B  a  section. 
In  Fig.  A  the  parallel  motion  is  shown,  which  is  now  made  of  drop-forged, 

compressed  steel.  The  paper  barrel  is 
very  light,  and  when  taking  off  the  paper 
barrel,  there  will  be  found  inside  a  milled- 
head,  above  which  is  a  thumb-screw,  shown 
in  Fig.  B.  The  spring  of  the  Improved 
Thompson  is  coiled,  in  Fig.  B,  into  the  sec- 
tion upon  which  the  end  of  the  pencil  lever 
touches ;  a  sleeve  runs  down  over  the 
spindle,  upon  which  is  a  hook,  and  that 
hook  engages  with  the  inner  coil  of  the 
spring.  By  loosening  the  thumb-screw 
shown  in  the  sectional  view  B,  and  grasp- 
ing firmly  the  milled-head  cover,  after  the 
I  paper  barrel  has  been  removed,  we  can  get 
any  amount  of  tension  required,  changing 
the  tension  according  to  the  speed  of  the 
engine  we  propose  to  indicate.  In  section 
B,  the  spring  is  shown,  the  inside  of  the 
piston  barrel,  with  an  universal  joint  which  engages  with  the  lever  at  the  top 
and  below  the  piston  of  the  instrument,  the  coils  of  the  spring  and  con- 
nection with  the  steam  cylinder — all  precisely  as 
they  are  found  in  the  instrument.  If  we  refer 
again  to  Fig.  A,  there  are  one  or  two  things  that 
need  to  be  noticed.  The  first  is,  that  the  parallel 
motion  of  this  instrument,  while  sufficiently 
strong  to  withstand  all  necessary  force  as  employ- 
ed, must  be  treated  with  care ;  sometimes  the 
springing  of  either  one  of  these  parts  will  make 
radical  errors  in  the  diagrams,  and  they  must 
always  be  carefully  lubricated.  When  applying 
the  pencil  to  the  paper,  we  do  not  use  the  little 
bone  handle  shown  in  both  A  and  B,  as  connected 
with  the  shank  which  holds  the  stand  of  the  par- 
allel motion,  which  brings  up  against  the  stop! 
shown  between  the  cylinder  of  the  indicator  and 
the  paper  barrel  in  both  Figures.  A  little  care 
right  here  will  save  a  great  deal  of  trouble,  inaccuracy  and  uncertainty.  The 
end  of  the  pencil  lever  is  split,  forming  a  shank  which  springs  down  upon  the 


FIG.  A. 


FIG.    B. 


TWENTY  YEARS  WITH  THE  INDICATOR.  5 

lead ;  after  the  lead  (leads  are  furnished  already  made)  is  pushed  into  this 
spring  shank  and  through  it  a  little  distance,  having  been  carefully  sharpened, 
then  adjust  this  bone  handle  by  means  of  the  screw  and  the  stop,  so  that  the 
end  of  the  pencil  shall  not  strike  against  the  paper  ;  but  when  we  wish  to  take 
a  diagram,  having  put  the  paper  on  the  paper  cylinder,  turn  on  steam,  then 
with  the  thumb  and  forefinger  grasp  this  bone  handle  firmly,  hold  it  against 
the  stop,  screw  it  until  you  feel  the  action  of  the  pencil  on  the  paper,  screw  it 
up  again  so  that  the  pencil  leaves  the  paper,  and  if  you  do  it  delicately,  you  will 
get  the  finest  possible  diagram  without  any  danger  of  injuring  or  cramping  the 
instrument.  Another  thing  which  should  always  be  done  :  get  the  diagram  as 
nearly  as  possible  in  the  center  of  the  paper  and  lead  off  the  cord  from  the 
pulleys  shown,  as  nearly  level  and  at  right  angles  as  possible.  Don't  turn 
them  around.  A  great  deal  of  distortion  comes  from  not  paying  attention  to 
the  hints  embodied  in  the  previous  clause  ;  sometimes  parties  who  cannot 
afford  to  be  delicate  in  their  manipulation  of  the  indicator,  bend  the  lever  by 
jamming  the  lead  against  the  paper  and  springing  it  perhaps  an  eighth  of  an 
inch  or  more.  That  is  sure  to  distort  some  of  the  lines  and  if  the  pencil  lever 
or  the  radial  bar  is  sprung,  then  the  instrument  must  go  back  for  careful 
overhauling  and  repair.  The  radial  bar  and  lever,  although  made  of  drop- 
forged  steel,  are  very  small,  and  while  they  are  strong,  they  will  not  do  with 
rough  usage,  and  yet  they  will  withstand  an  amount  of  abuse  that  one  might 
wonder  at,  after  having  examined  them. 

HOW  AND  WHERE  TO  ATTACH  THE  INDICATOR. 

There  is  always  a  clearance  in  any  engine  we  have  ever  yet  seen.  This 
is  a  space  between  the  piston,  when  it  is  at  the  extreme  range  of  stroke,  and 
the  cylinder  head  ;  this  is  variously  estimated  and  in  different  engines  varies 
materially  in  proportion  of  percentage  to  the  whole  volume  of  the  cylinder. 
Wherever  the  indicator  is  attached  there  must  be  a  clear  way  into  the  clear- 
ance, so  that  the  piston  shall  not  shut  it  off,  even  partially,  when  at  the  extent 
of  its  stroke.  The  usual  connection  is  a  half-inch  gas  pipe  or  steam  pipe,  and 
if  this  is  carried  out,  it  is  quite  large  enough  ;  whenever  the  engine  is  indi- 
cated, make  sure,  among  other  things,  at  the  very  outset  by  "  turning  her 
over  "  that  no  part  of  the  piston  travels  over  the  connection  into  the  clear- 
ance ;  if  so,  one  of  two  things  must  be  done,  either  drill  another  hole — and 
this  is  not  always  practicable — or  take  a  chisel  with  point  so  that  you  can 
break  off  the  inside,  and  give  fully  the  area  of  a  half -inch  pipe  without  any 
possibility  of  obstruction  or  reduction.  Always  endeavor  when  tapping  an 
engine  to  tap  it  so  as  to  use  the  pantograph,  remembering  that  the  panto- 
graph can  be  used  vertically,  so  as  to  make  your  connections  on  the  top  of 
the  cylinder  sometimes,  or  horizontally  so  as  to  make  them  on  the  side.  It 
is  best  to  make  these  connections  between  the  ports  rather  than  opposite 
them,  but  sometimes  there  is  no  choice.  Whenever  these  openings  are  made, 
take  particular  care  that  the  inside  end  is  clear,  either  with  the  chisel  or  rim- 
mer,  else  you  have  a  factor  of  uncertainty.  It  is  a  frequent  practice  with 


6  TWENTY  YEARS  WITH  THE  INDICATOR. 

many  builders  of  the  very  late  years,  to  furnish  what  is  called  a  side-pipe  and 
three-way  cock  with  each  engine.  The  whole  thing  is  to  be  condemned,  un- 
less an  approximation  is  wanted  for  the  load,  for  the  position  of  the  valves, 
etc.,  and  if  our  readers  will  turn  to  Lessons  LVI,  and  LYII,  Figs.  116  and 
117,  they  will  have  a  chance  to  see  the  position  of  the  valves  as  shown  by  the 
three-way  cock  and  side-pipe  in  one  case,  and  the  short  connections  in  the 
other  case,  nothing  having  been  moved,  so  far  as  the  valves,  eccentrics,  etc., 
were  concerned.  On  marine  engines  it  is  very  fashionable  (for  we  know  no 
other  reason  for  it)  to  take  an  inch  and  a  quarter,  or  inch  and  a  half  pipe,  lead 
it  from  the  clearance  at  either  end  to  the  most  convenient  part  of  the  cylinder, 
back  of  the  side-pipes,  and  there  put  in  the  three-way  cock.  We  have  seen 
and  used  this  upon  condensing  engines  with  12  and  14  feet  stroke,  and*  in 
one  case  where  the  steam  line  figured.  3§  inches  of  the  length,  by  the  propor- 
tion of  stroke  on  the  diagram,  the  engineer  had  the  curiosity  as  well  as  good 
sense  to  strip  his  side-pipe ;  two  days  afterwards  we  applied  the  indicator 
with  short  connections  showing  that  the  valves  were  open  at  the  very  com- 
mencement of  the  stroke  and  the  steam  line  did  not  vary  one-half  of  one  inch 
when  the  short  or  proper  connection  was  made,  yet  in  traveling  several  feet 
it  showed  late,  for  the  paper  barrel  started  when  the  piston  started,  but  the 
steam  traveled  from  the  clearance  through  the  various  angles  and  ports  of  the 
cock  into  the  indicator  with  whatever  little  condensation  took  place  on  the 
way,  so  that  the  motion  was  distorted  3f  inches  from  the  truth  ;  this  makes 
a  difference  in  the  pressure  of  steam  as  well,  so  that  it  may  be  laid  down  as  a 
rule,  to  avoid  three-way  connections  if  the  real  position  of  the  valves  is  of  any 
consequence,  or  if  the  actual  condition  of  the  valves  is  to  be  learned  from  the 
diagrams.  Several  instances  of  side-pipes  are  shown  in  this  volume,  some  of 
these  would  be  very  dangerous  if  the  valves  were  adjusted  to  bring  the  steam 
lines  up  at  right  angles  to  the  atmospheric  line  and  still  use  the  side-pipe.  It 
would  be  apt  to  result  in  something  quite  similar  in  effect  to  that  shown  in 
Lesson  LXIX,  Fig.  135. 

It  is  sometimes  impossible  to  use  the  short  connection,  but  wherever  it 
can  be  done,  it  is  decidedly  better  to  do  it,  if  accuracy  is  any  sort  of  a  condi- 
tion towards  which  you  are  aiming  for  results.  Avoid  elbows  and  valves  in 
feed-pipes  and  exhaust-pipes  as  much  as  possible,  always  remembering  one  of 
the  fundamental  laws  of  all  engineering,  viz.  :  that  the  shortest  possible  dis- 
tance from  any  given  point  to  another  is  a  straight  line,  so  remember  that 
in  handling  steam  the  utmost  economy  attainable  wherever  steam  is  conveyed 
through  pipes,  is  invariably  accomplished  by  taking  the  steam  as  direct  as 
possible  and  avoiding  every  impediment  or  obstruction,  such  as  is  offered  by 
globe  valves,  reducing  valves,  throttle-valves,  elbows,  crosses,  T's,  or  other 
angles,  through  which  steam  must  pass  in  order  to  reach  the  piston  head. 
Anything  which  interrupts  the  flow  of  steam  causes  friction,  loss  of  pressure ; 
and  in  every  case  where  the  pressure  of  steam  is  reduced,  its  volume  is  in- 
creased and  it  takes  the  first  step  towards  the  convemon  from  steam  into 
water  again. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


A  POINT  AS  TO  HOW  TO  MAKE  THE  LEAD  DO  GOOD  WORK. 

It  is  much,  better  to  sharpen  the  lead  before  being  put  into  the  spring 
shank  in  the  end  of  the  lever,  by  means  either  of  a  scythe-stone  or  dry  oil- 
•  stone,  or  if  nothing  better  is  at  hand  take  a  fine  file.  A  point  which  is  rubbed 
up  in  this  way,  and  made  smooth  and  clean,  will  last  much  longer,  make  a 
cleaner  mark  and  be  much  better  than  one  which  is  whittled  or  coarsely  done. 
The  best  way  is  always  the  easiest,  the  surest  and  the  cheapest,  all  things 
taken  into  account.  There  is  no  necessity  for  running  over  a  large  number 
of  times.  This  much  for  the  manipulation  of  the  instrument. 

Having  attached  the  indicator  to  the  side  pipes,  which  must  in  all  cases 
be  blown  out  thoroughly  and  completely  before  applying  the  indicator,  be 
careful  not  to  employ  joints  with  red  lead  or  white  lead  or  any  other  material 
which  can  possibly  interfere  with  the  action  of  the  piston ;  then  adjust  the 
indicator  to  the  top  of  the  cocks,  screw  down  the  variable  screw,  having  first 
put  the  indicator  as  nearly  in  line  with  the  motion  as  is  possible,  make  sure 
that  all  is  fast  and  then  let  the  steam  on  to  the  instrument  gently,  warm  it 
up,  allow  all  the  water  to  get  out  so  far  as  possible.  While  the  instrument 
is  working  put  a  drop  or  two  of  porpoise  oil  on  to  the  top  of  the  piston  as  it 
comes  through  the  cover  of  the  case;  repeat  this  occasionally.  Now,  try  the 
motion  with  the  pantograph,  pendulum  or  whatever  else  may  be  used,  and 
carefully  adjust  it  for  the  stop.  The  paper  cylinder  must  not,  on  any  account, 
touch  either  end  of  the  travel  against  the  stop,  even  so  slightly  as  not  to  be 
noticeable,  for  it  will  distort  some  line  of  the  diagram  as  sure  as  it  does. 
Having  balanced  the  instrument,  as  we  term  it,  you  are  now  ready  to  go 
ahead.  In  taking  a  diagram,  don't  work  with  dirty  hands  ;  you  are  sure  to 
dirty  the  instrument,  and  the  diagrams  look  as  though  they  had  been  in  the 
hands  of  a  careless  man.  Putting  the  paper  about  the  cylinder  is  a  little 
knack  in  itself.  The  paper  should  go  down  square,  fit  as  close  as  a  glove, 
and  be  just  as  clean  as  though  it  had  never  been  touched ;  a  little  practice  is 
required.  Having  accomplished  all  this,  let  the  steam  in ;  don't  take  the 
diagram  until  after  the  instrument  is  heated.  Take  the  diagram  first  as  per 
previous  directions,  shut  off  the  steam,  being  careful  not  to  allow  any  steam 
to  blow  through  the  three-way  cock,  and  the  moment  this  is  closed  tightly 
then  take  the  atmospheric  line  while  all  parts  of  the  instrument  are  warm.  If 
the  atmospheric  line  is  taken  before  the  instrument  is  thoroughly  warmed  up, 
it  will  be  incorrect ;  if  it  is  taken  after  contraction  has  taken  place  by  cooling 
off,  even  some  time  after  the  diagram,  it  will  then  be  incorrect.  Take  the 
diagram  first,  the  atmospheric  line  afterwards ;  then,  having  noted  the  steam 
pressure,  knowing  the  dimensions  of  the  engine  in  diameter  and  stroke,  and 
number  of  strokes  or  revolutions,  put  all  this  data  carefully  upon  the  proper 
place  in  the  card ;  be  sure  and  add  to  it  the  scale  and  any  memoranda  which 
are  necessary,  and  you  will  have  progressed  systematically ;  and  if  you  have 
followed  the  directions  given  for  handling  the  pencil,  you  will  have  produced 
a  beautifully-drawn  diagram,  which  will  give  you  the  correct  working  of  the 


8  TWENTY  YEARS  WITH  THE  INDICATOR. 

steam,  the  position  of  everything  and  its  relation  to  the  economical,  or  other- 
wise, handling  of  the  steam. 

THE  STEAM  WHICH  A  SPRING  WILL  TAKE. 

The  American  Steam  Gauge  Company  give  their  rule  as :  Multiply  the 
scale  of  the  spring  by  2 \  and  subtract  15 ;  the  result  will  be  pounds  of  steam 
pressure  from  the  vacuum  line  that  the  spring  will  take  accurately ;  as,  for 
instance,  30x2^=75—15=60.  We  think  this  might  be  changed  with  benefit, 
for  it  is  not  always  necessary  to  provide  for  the  15  pounds  vacuum,  and  it  is 
desirable  always  to  make  the  indicator  diagram  as  large  as  can  be.  For  this 
purpose  we  adopted  some  years  since  the  practice  of  having  a  set  of  washers 
made,  which  would  slip  on  to  the  sleeve  under  the  cover  on  top  of  the 
indicator  piston  cylinder,  or  upon  the  shank  of  the  piston  itself  at  the  bottom, 
and  these  washers  vary  in  thickness  from  -fa  of  an  inch  to  J  of  an  inch.  By 
these  means  we  can  take  75  pounds  of  steam  with  a  30  spring  by  first  block- 
ing down  the  pencil  lever ;  instead  of  standing,  as  shown  hi  Fig.  A,  it  will 
stand  nearer  the  bottom  of  the  paper  cylinder  when  at  rest.  There  are  two 
things  to  be  guarded  against :  never  under  any  circumstances  undertake  to 
indicate  a  pressure  of  steam  which  shall  be  beyond  the  capacity  of  the  spring; 
for  in  the  one  case  you  will  bring  up  solid,  and  in  the  other  case,  at  the  top, 
you  will  throw  the  pencil  lever  out  of  a  parallel  line  by  passing  beyond  its 
capacity,  and  get  something  which  may  appear  to  you  like  Fig.  135  in  this 
Tolume.  It  will  distort  the  lines  and  not  do  the  instrument  any  good. 

The  best  oil  that  we  can  obtain  is  pure  porpoise  jaw  oil;  ordinary 
mineral,  fl.Tnmn.1  or  vegetable  oils  are  affected  more  or  less,  and  the  porpoise 
oil,  which  is  worth  a  good  many  dollars  a  quart,  only  requires  a  very  small 
amount  if  you  use  it  carefully;  this  should  be  used  on  all  parts  of  the 
indicator.  » 

Before  we  leave  the  subject  of  springs,  it  may  be  proper  to  state  that 
the  softest  spring  which  can  be  used,  and  keep  within  the  limits  of  its  capacity, 
is  the  spring  in  every  instance  that  you  should  use.  The  practice  is  becoming 
quite  common  among  parties  in  this  country  of  using  50  and  60  springs,  and 
in  other  places  of  using  a  small  diagram,  the  smaller  the  better.  In  every 
case  keep  clear  of  this  kind  of  practice.  The  larger  the  diagram,  the  more  the 
faults  of  the  instrument  are  shown,  if  there  are  any,  and  the  more  the  faults 
of  the  engine  builder,  if  he  has  been  careless  in  his  construction.  The  only 
case  where  we  advocate  the  small  diagram  is  with  engines  running  above  300 
or  350  revolutions.  This  will  be  referred  to  later.  The  smaller  the  diagram, 
the  less  real  reliance  is  to  be  placed  upon  it,  and  the  cause  of  this  will  be 
found  in  some  of  the  lessons  on  high  speed,  where  different  diagrams  are 
referred  to,  and  the  real  reason  why  the  larger  scales  should  be  always  used 
will  be  found  with  a  little  reasoning. 


TWENTY  YEARS  WITH  THE  INDIGA  TOE.  9 


CHANGING  THE  SPRING. 

It  is  frequently  necessary  while  working  upon  an  engine,  for  some  reason 
or  other  to  change  the  spring  with  varying  pressure,  speed,  or  some  other  re- 
quirement. There  is  no  reason  why  this  cannot  be  done  in  about  one  minute, 
providing  you  have  the  spring  where  it  is  wanted,  and  understand  your  work 
and  are  careful  about  it,  and  there  is  no  instrument  we  have  ever  seen  that 
begins  to  compare  with  the  Thompson  for  accessibility.  Having  decided,  you 
must  change  the  spring,  commence  with  the  connection  of  the  top  of  the 
piston  with  the  pencil  lever,  taking  out  the  little  milled-head  screw,  then  re- 
lease the  pencil  bar  from  the  piston,  taking  notice  that  the  ears  on  the  piston 
connection  have  a  screw-thread  in  one  and  a  clear  hole  in  the  other  side  ;  hav- 
ing separated  these,  then  unscrew  the  cover  to  the  piston  casing,  lift  the 
whole  thing  off,  piston,  spring,  cover,  pencil  lever,  etc.  Be  careful  never  to 
drop  the  piston  upon  a  gritty  floor,  rather  take  it  in  your  handkerchief  or 
some  other  clean  cloth ;  now  unscrew  the  piston  from  the  under,  side  of  the 
cover,  the  spring  from  the  lower  end  of  the  piston,  put  on  the  other  spring, 
screw  it  on  to  the  shank  on  the  upper  side  of  the  piston,  put  it  through  the 
casing,  screw  the  shank  of  the  cover  into  the  top  of  the  spring ;  now  put  the 
top  of  the  connecting  rod  so  that  the  pencil  lever  will  easily  drop  between 
the  two  ears,  adjust  the  screw  which  passes  through  one  ear,  then  through 
the  pencil  bar,  and  screw  into  the  other  ear  on  the  top  of  the  connection  rod ; 
screw  the  cover  into  the  casing,  after  having  put  a  drop  of  oil  on  the  piston, 
and  see  that  it  works  easily  back  into  the  casing,  and  that  the  piston  drops 
easily  into  the  cylinder  and  the  cover  goes  down  into  the  casing  all  easy 
together,  and  that  the  pencil  lever,  parallel  bar  and  radial  lever  are  all  easy 
and  none  of  them  are  sprung,  having  previously  taken  care  that  the  connec- 
tions are  all  blown  out,  so  that  no  dirt  can  be  blown  into  the  indicator  from 
any  of  the  connections.  This  can  all  be  done  in  less  time  than  it  has  been 
written  in.  You  are  now  ready  to  go  ahead. 

GENERAL  HINTS. 

Sometimes,  in  taking  the  indicator  off  from  the  steam  connection,  it  may 
receive  a  jar  in.  such  a  way  that  the  stand  which  connects  the  piston  barrel 
and  the  paper  barrel  together  may  be  sprung.  We  have  sometimes  found 
this  to  be  done.  There  is  no  necessity  for  it ;  it  should  never  occur.  If  it 
occurs,  and  you  are  out  of  reach  of  help,  you  may  take  the  thing  in  your  own 
hands ;  but  never  take  a  diagram  unless  your  pencil  bar  describes  an  absolute 
right  angle  line  to  the  atmospheric,  and  then  it  is  a  good  plan  when  this 
occurs  to  send  it  back  to  the  shop  to  be  put  into  the  jig  and  examined.  It 
may  have  a  crosswise  spring,  and  except  a  diagram  is  accurate  it  is  value- 
less. 

The  Thompson  Improved  Indicator  succeeds  the  Richards'  Indicator, 
which  has  worked  a  revolution  in  engine  building.  When  speed  and  other 
matters  of  importance  came  up,  Mr.  J.  W.  Thompson  patented  the  parallel 


10 


TWENTY    YEARS     WITH    THE    INDICATOR. 


motion,  not  shown,  for  it  has  now  practically  been  discarded,  and  has  been 
displaced  by  the  Improved  Thompson,  shown  in  Fig.  A.  This  instrument  is 
manufactured  solely  in  the  United  States  by  the  American  Steam  Gauge 
Company,  Boston. 

GIVING    TrtE    MOTION. 

Leaving  Figs.  A  and  C,  a  peculiar  device  is  seen,  for  the  lack  of  which 
there  has  been  much  trouble  in  times  past.  Fig.  D  shows  an  improved 
method  of  taking  the 
motion  off  the  paper 
barrel.  A  represents 

the  wheel,  which  is  xa^B^k.^Wr ^^-^^  W&^^^s^^^^^^^. 
also  shown  in  dotted 
lines  in  a  different  po- 
sition ;  B  represents 
a  stand  holding  the 
wheel  over  which  the  FIG.  D. 

cord  passes ;  and  the  end  of  the  stand  is  a  sleeve  running  into  the 
solid  stand  shown,  the  whole  thing  being  bored  through ;  and  the  flat 
part  shown  at  the  right  is  secured  against  the  bottom  of  the  stand  by 
means  of  a  thumb-nut  at  the  lower  end  of  A,  B,  C.  The  sleeve  which 
extends  into  this  stand  has  in  its  center  a  groove  into  which  the  flat- 
headed  thumb-screw,  C,  enters,  holding  it  in  any  position,  to  the  right  or  the 
left,  up  or  down,  giving  it  the  full  swing  of  the  whole  circle,  and  in  this  way 
the  motion  can  be  taken  from  any  point,  at  almost  any  angle  that  it  is  possible 
in  the  whole  360°,  either  horizontally  or  vertically.  It  is  one  of  the  improve- 
ments made  by  the  Steam  Gauge  Company  within  the  last  two  years,  and  is 
the  subject  of  separate  patents.  Wherever  the  old  plan  of  wheels  is  in  use 
on  the  old  Thompson  or  the  Improved  Thompson,  this  can  be  substituted  if 
required.  All  instruments  now  made  are  made  with  the  device  shown  in  Fig. 
D,  and  this  device,  as  simple  as  it  is,  makes  it  possible  to  use  the  instrument 
in  many  places  where  special  motions  had  to  be  arranged  by  the  old  method. 

AMERICAN  STEAM  GAUGE  COMPANY'S  AMERICAN  IMPROVED  DETENT 

MOTION  INDICATOR. 

On  page  IOA  is  shown  the  new  form  of  the  Detent  Motion,  changed  in 
this  edition  of  this  book  for  the  first  time  since  the  first  copy  was  printed. 
Fig.  C  shows  the  front  view  of  the  regular  Thompson  Indicator  with  a 
2  inch  diameter  paper  cylinder,  which  is  used  up  to  300  R.  P.  M.  The 
Detent  Motion  is  also  applicable  to  their  regular  high  speed  Improved 
Thompson  Indicator,  having  a  i^  inch  diameter  paper  cylinder.  The  \y2 
inch  diameter  cylinder  gives  a  diagram  4  inches  long ;  the  2  inch  diameter 
cylinder  gives  a  diagram  5  inches  long.  Otherwise  than  that  the  smaller 
cylinder  is  used  for  the  higher  speeds,  there  is  practically  no  difference 
between  the  two  mentioned  instruments. 


TWENTY    YEARS     WITH    THE    INDICATOR.  JOA 

The  distinctive  difference  between  the  Improved  Detent  Motion  Indi- 
cator and  the  old  Detent  Motion  Indicator  made  years  ago,  is,  that  the  base 
piece  around  which  the  cord  goes,  which  takes  its  motion  from  the  crosshead 
of  the  engine  gives  motion  to  the  paper  cylinder  above  it,  -  can,  by  the 

movement  of  the  lower  or  right-hand 
lever  shown  in  the  cut,  be  separated 
instantly  from  the  paper  cylinder,  leav- 
ing the  cylinder  standing  perfectly  still, 
and  this  is  done  without  any  shock 
either  to  the  cord,  to  the  reducing  mo- 
tion, or  the  paper  cylinder.  When1  the 
paper  cylinder  is  stopped  by  this  move- 
ment, it  assumes  the  proper  position1, 
as  shown  in  the  cut,  by  means  of  a 
spring  inside  of  it,  described  later  on, 
and  brings  the  paper  springs  in  front 
or  always  in  the  same  place,  so  the 
fresh  paper  can  be  put  on. 

The  upper  handle  shown,  is  con- 
nected to  the  movable  stand  which  car- 
FIG-  c«  ries  the  pencil  motion  around,  and  con1- 

nected  to  the  steam  piston,  and  has  nothing  whatever  to  do  with  any  other 
part  of  the  instrument. 

When  the  lower  lever  is  moved  to  the  right,  and  the  connection  cut 
between  it  and  the  paper  cylinder,  the  motion  is  continued,  no  matter  what 
the  speed  of  the  engine  is,  and  the  cord  and  the  reducing  motion  keep  right 
on  about  their  business.  When  the  lever  is  moved  to  cut  the  paper  cylinder 
free  from  the  motion,  the  paper  cylinder  lacks  a  little  of  the  point  of  contact, 
and  whenever  the  operator  desires  to  start  the  paper  cylinder  again,  he  takes 
hold  of  the  knurled  head  on  the  top  of  the  paper  cylinder,  and  turns  it,  per- 
haps one-eighth  inch,  when  the  connection  is  made  automatically,  and  you 
are  then  ready  to  take  a  diagram.  This  last  mentioned  arrangement  prevents 
the  taking  of  diagrams  when  you  don't  want  them,  and  insures  the  taking  of 
them  when  you  do  want  them,  and  it  is  very  neatly  worked  out  in  the  instru- 
ment. 

When  the  paper  cylinder  is  stopped,  it  will  stand  perfectly  still.  It 
cannot  catch  and  disappoint  the  operator.  The  diagram  can  be  examined, 
taken  off,  changed,  or  the  same  one  may  be  started  again,  as  above  directed, 
and  the  whole  thing  is  in  the  hands  of  the  operator. 

The  Detent  motion  in  this  case  avoids  a  great  many  of  the  troubles 
incident  to  the  older  fashioned  methods  of  combining  a  Detent  motion  with 
a  steam  engine  indicator.  There  would  seem  to  be  no  possible  chance  in 
this  for  the  breaking  of  cords,  pulling  out  hook,  smashing  the  pencil  motion 
by  the  Detent  motion  engaging  when  it  was  wanted  to  be  kept  free,  or  in 


10B 


TWENTY    TEARS     WITH    THE    INDICATOR. 


not  getting  the  diagram  because  the  Detent  motion  did  not  engage  at  the 
instant  of  time  when  it  was  expected  to  do.  These  old-time  troubles  would 
seem  to  have  disappeared  entirely.  The  whole  thing  is  so  simple  that  it 
might  have  been  discovered  many  years  ago,  and  could  have  been  put  into 
operation  long  ago,  to  the  advantage  of  people  who  are  unaccustomed  to 
handling  indicators  at  a  rapid  speed. 

This  particular  indicator  would  seem  to  be  exceedingly  desirable  in  a 
great  many  places  around  marine  engines,  locomotive  engines,  or  other 
places  where  an  instrument  must  be  attached  in  such  a  place  or  at  such  a 
point  that  it  is  not  only  very  unpleasant  getting  to  it  and  away  from  it,  but 
frequently  the  amount  of  room  is  exceedingly  limited  and  in  too  close  prox- 
imity to  very  hot  pipes  or  surfaces.  This  attachment  may  be  applied  to 
either  hand  indicator,  and  in  almost  any  position  that  it  is  possible  to  put  it ; 
if  the  paper  barrel  of  the  instrument  is  in  a  horizontal  position  rather  than 
in  a  vertical  one,  the  Detent  is  just  as  reliable  and  fully  as  serviceable ;  or  if 
you  get  into  close  quarters  with  it,  it  would  seem  to  have  every  facility  that 
it  was  possible  to  combine  in  such  a  small  piece  of  mechanism,  which  is  so 
very  important. 

One  of  the  most  important  things  sug- 
gested to  the  writer,  is  that  by  this  particular 
application  of  the  Detent  motion,  the  taking  off 
of  the  paper  cylinder  is  positively  and  unequiv- 
ocally done  away  with. 

It  has  been  a  great  bugbear  to  engineers 
using  Detent  indicators  that  it  was  necessary  to 
catch  the  paper  cylinder  at  almost  the  right 
point  in  the  stroke,  or  break  a  cord,  or  do  some 
other  mischief  which  required  time,  and  often 
a  great  deal  of  trouble,  to  put  again  into  proper 
form.  The  paper  cylinder  of  this  instrument 
cannot  be  taken  off  without  unscrewing  the 
thumb-nut  at  the  top,  and  the  only  necessity  for 
taking  it  off  at  all  is  to  clean  and  oil  the  long- 
bearing  on  the  inside. 

Fig.  C2  shows  the  interior  mechanism. 
"  Remove  the  knurled  nut  F ;  take  off  the  paper 
cylinder,  and  with  a  wire  clip,  (sent  with  each 
indicator) ,  remove  the  auxiliary  spring  case  H 
by  catching  the  end  of  the  clip  in  the  notches  of 
the  spring  case ;  turn  it  forward  until  it  releases  from  the  catches ;  then 
remove  the  spring  and  the  inner  sleeve  I ;  clean  and  oil ;  replace  the  inner 
sleeve  I,  by  inserting  into  the  cylinder  so  the  pin  on  the  outside  of  the  sleeve 
will  enter  the  slot  inside  of  the  cylinder  bearing.  Turn  it  until  it  comes  to  a 
stop ;  then  with  the  clip  catch  the  auxiliary  spring  holder  H  and  give  the 


FIG.    C2. 


TWENTY     YEARS     WITH    THE    INDICATOR.  U 

spring  E  a  tension  of  about  ^  of  a  turn,  and  catch  the  points  on  the  spring 
case  H  into  the  slots  provided  for  them."  These  are  the  maker's  directions. 

The  paper  cylinder  has  a  spring  which  brings  it  back  to  its  proper  position 
independent  of  the  spring  which  looks  after  the  cord  on  the  reducing  motion. 
The  thing  is  very  simple,  very  positive.  The  small  paper  cylinder  instru- 
ment uses  the  same  spring,  pencil,  levers,  pistons,  and  fittings  that  the 
larger  instrument  does.  Several  hundred  of  these  instruments  are  now  in 
use,  and  with  the  very  best  satisfaction. 

The  instrument  with  2  inch  diameter  paper  cylinder,  or  No.  i  indicator, 
is  adapted  for  speeds  up  to  300  r.p.m.  At  that  speed  it  will  take  a  diagram 
4^  inches  or  4^4  inches  long.  The  instrument  with  i^  inches  diameter 
paper  cylinder,  or  No.  2  indicator,  will  take  a  diagram  3^  inches  or  3^ 
inches  in  length  up  to  650  or  even  700  r.p.m. 

METHOD    OF   ATTACHING    THE   INDICATOR,    OR    OF   MAKING    UP    THE 

REDUCING   MOTION. 

There  is  probably  no  one  device  which  has  been  used  so  much  as  the  old 
pendulum,  and  there  is  no  device  which  is  so  generally  incorrect  or  so  much 
misapplied.  These  pendulums  have  various  faults,  and  the  usurs  of  them 
have  many  vagaries.  We  recently  saw  in  a  large  engine-room  a  pendulum 
attached  to  a  piece  of  iron,  leading  from  one  girder  to  another  in  a  fire-proof 
arched  floor,  and  it  is  no  exaggeration  to  say  that  the  top  of  the  pendulum 
chattered  from  an  eighth  to  a  quarter  of  an  inch  sidewise,  while  the  strap 
which  passed  from  one  girder  to  the  other  jumped  up  and  down  as  much  more, 
making  a  most  peculiar  motion.  The  string  was  then  taken  off  at  an  angle  of 
10°  or  15°,  brushing  by  the  side  of  the  steam-pipe,  and  was  deflected  from 
the  straight  line  between  the  carrier  pulley  above  and  the  indicator  pulley 
below  more  than  one  inch.  It  was  perfectly  useless  to  attempt  to  show  the 
party  using  it  that  he  had  errors  multiplied  by  each  other  into  an  outrageous 
accumulation,  and  that  his  diagram  was  worse  than  worthless  for  any  purpose 
whatever.  The  pendulum  can  be  used.  It  must  be  firmly  fixed  at  the  top, 
it  must  be  strong  enough  in  its  cross  section  not  to  spring  either  edge-wise 
or  flat-wise ;  the  bottom  of  the  pendulum  must  in  every  case  start  from  the 
actual  center  of  motion,  it  must  travel  precisely  as  far  one  side  of  this  center 
of  motion  as  the  other  and  not  an  iota  farther  one  side  than  the  other ;  in 
other  words,  it  must  be  exact.  If  these  simple  precautions  are  heeded,  then 
the  pendulum  becomes  endurable,  but  in  taking  off  the  cord  it  must  not  be 
taken  from  a  point  near  the  top  at  an  angle  anywhere  from  1°  to  120°,  down 
to  the  indicator  direct  on  the  cylinder.  It  must  be  taken  at  right  angles  to 
the  central  line  of  the  pendulum  when  at  rest,  to  a  point  over  the  indicator, 
and  if  only  one  instrument  is  to  be  used,  the  carrier  pulley  may  be  placed  on 
a  line  plumb  over  the  center  of  the  cylinder,  so  that  the  cord  leaving  the  pen- 
dulum shall  leave  it  at  right  angles  absolutely  when  it  hangs  plumb,  and  pass- 
ing over  the  pulley,  there  is  no  necessity  then  for  continuing  this  exactness. 


12 


TWENTY  YEARS  WITH  THE  INDICATOR. 


FIG.    E. 

screw-thread   at   the   bottom 
in 


for  a  little  to  the  right  or  left  of  plumb  in  that  case  does  not  distort  the 
motion  ;  but  if  the  first  portion  is  not  at  right  angles,  then  we  get  distortion 
of  the  worst  kind.  The  pendulum  may  be  inverted  by  the  same  precautions, 
as  it  is  sometimes  impossible  to  get  a  pantograph  between  the  cross-head  and 
the  .side  of  the  wall ;  or  we  have,  in  some  cases  where  we  could  not  use  either 
on  account  of  too  much  distance  at  one  end  and  too  little  at  the  other,  laid  a 
pendulum  on  its  side  ;  most  men  would  not  take  pains  with  this  and  we  do 
not  therefore  advise  it. 

Instead  of  the  old  means  of  attaching,  Fig.    E   shows  what  is  known  as 
Bacon's  Improvement,  being  a  combination  patented  by  our  old  friend  F.  W. 

Bacon,  made  by  the  American  Steam  Gauge 
Company,  consisting  of  five  pieces  ;  the  joint- 
ed links  at  the  right  are  intended. that  the 
longer  parts  should  be  put  under  the  check- 
nut  of  the  oil  cup  to  which  it  may  be  attached 
on  the  cross-head  ;  the  shorter  parts  turn  over 
each  other  according  as  the  longer  parts  may 
be  farther  apart  or  nearer  together,  until  the 
holes  match,  through  which  the  screw-thread 
shank,  shown  at  the  top  with  a  hole  through 
it,  may  be  used  for  the  pantograph,  or  the 
may  pass  through  this  'hole  and  be  used 

the  pendulum,  as  is  shown  in  Fig.  F.  There  are  a  great  many  ways 
of  attaching  this  to  different,  engines  which  will  be  followed  up.  Fig. 
E  s-hows  the  parts  in  detail,  Fig.  F  shows  them  attached  to  a  pendu- 
lum, Fig.  G  shows  the  top  of  a  post,  pantograph,  and  the  Bacon 
attachment  connected  to  a  vertical  cross-head,  although  the  cross-head 
is  not  shown,  it  simply  shows  the  method  of  attachment.  Fig.  H  shows 
the  pantograph  attached  to  a  vertical  cross-head  and  the  pieces  are 
attached  to  the  shoe  at  the  bottom  by 
simply  raising  up  the  nut  which  holds 
the  slide  in,  and  then  gripping  them 
by  screwing  down  upon  them  again.  In 
both  of  these  methods  of  attaching 
the  pantograph,  bear  in  mind  the 
rule  with  reference  to  the  pantograph. 
The  post  on  the  outside  must  be  set 
at  exactly  right  angles  to  the  center 
of  motion  when  at  rest ;  in  other  words 
the  pantograph  must  travel  precisely 
as  far  one  side  as  the  other  of  the  center  of  motion,  and  not  as  we 
have  sometimes  seen  it,  forming  the  hypothenuse  of  a  right  angled 
triangle,  working  all  the  distance  one  way.  Fig.  I  shows  another  method  of 
connection  to  the  Corliss  cross-head,  to  which  all  the  same  rules  apply.  Fig. 
J  shows  the  pantograph  and  the  Bacon  attachment  connected  to  a  horizontal 
cross-head. 


FIG.  F. 


G. 


TWENTY  YEARS  WITH  THE  INDICATOR.  18 


RULE  FOR  THE  PANTOGRAPH. 

In  all  these  attachments  of  the  pantograph,  whether  horizontal  or  veiv 
ticai  (and  the  pantograph  can  be  used  as  well  vertically  as  horizontally,  if  a 

little  care  be  used  in  attach- 
ing it,  being  the  simplest 
and  the  most  correct  of  all 
the  motions  known),  let  the 
pantograph  be  attached  as 
shown  in  Fig.  0,  whether 
it  be  the  center  of  the  cross- 
head  or  one  end  of  the 
cross-head  is  entirely  im- 
material, but  let  that  point 
FIG>  H-  at  which  it  is  attached  be 

invariably  the  exact  center  of  motion.  Set  the  out-post  square  with  the  center 
of  motion,  and  in  no  other  place  or  position.  Now,  as  the  stroke  of  the  engine 
varies  it  is  necessary  to  get  more  or  less  motion,  which  can  be  done  by 
moving  the  peg-post  or  peg  arm  out  or  in  on  this  line,  which  has  been  drawn 
squarely  across  with  the  center  of  motion.  Let  the  line  from  the  peg-post  to 
the  indicator  be  at  a  right  angle  to  the  center  of  motion,  or  in  other  words,  let 
the  line  which  connects  the  peg-post  of  the  pantograph  with  the  paper  drum  ol 
the  instrument,  be  as  nearly  parallel  with  the  piston  rod  as  it  is  possible  to 
get  it.  If  these  two  simple  rules  are  observed,  any  engineer  can  obtain  a 
diagram  which  is  mechanically,  geometrically,  and  mathematically  as  correct 
as  any  other  man  on  earth  can  do  it.  We  have  frequently  said  before  differ- 
ent audiences,  written  it  ovei  and  over  again :  the  indicator  diagram,  the  valve 
motion,  the  pantograph  or  the  pendulum,  are  only  and  simply  a  combination 
of  right  angles.  If  everything  is  done  exactly  on  the  square,  everything  else 
will  be  exactly  right,  whether  you  are  working  for  the  position  of  valves,  use 
of  steam  or  anything  else ;  the  indicator 
diagram  in  this  case  with  these  two  sim- 
ple rules  observed,  will  be  a  positive 
quantity,  perfectly  reliable,  and  if  these 
two  rules  are  not  observed,  it  is  as  per- 
fectly and  as  completely  worthless  as 
it  is  possible  to  be. 

Fig.  K  represents  the  pantograph 
more  in  detail,  with  letters  of  reference. 
This  simple  arrangement,  like  so  many 
other  things,  we  are  indebted  to  George  IG< 

H.  Corliss  for.  It  has  a  great  variety  of  names ;  it  has  been  called 
"lazy  tongs,"  "long  legs,"  " pantograph  ;"  it  was  originally  called  and  we 
believe  Mr.  Corliss  himself  terms  it  his  "  drum  motion."  It  consists  of 
nothing  more  or  less  than  a  system  of  levers  ;  these  levers  must  be  absolutely 


TWENTY  YEARS  WITH  THE  INDICATOR. 


of  the   same  length,  those  shown  at  A  being  double  and  those  at  B  being 
single.     These  are  pivoted  by  means  of  hollow  pivots  and  washers  which  are 

bushed.  The  hitch  strip  is  shown  at 
G  and  the  stud-pin  or  hitch-pole  F. 
When  the  pantograph  is  properly  ar- 
ranged the  stud-pin  F  is  in  the  line 
between  C  and  D,  which  are  the  two 
ends  of  the  pantograph,  one  being  the 
dead  end  D,  which  is  fastened  to  the 
post,  while  C  is  the  live  end  or  at- 
tached to  the  cross-head  of  the  engine. 
The  point  C  attaches,  where  Fig.  E  is 
used,,  to  the  two  links  connected  to- 
gether, so  that  the  pin  at  the  end,  C, 
readily  drops  through  them.  If  the 
links  have  to  be  used  so  that  they  stand 
vertically,  then  the  little  screw-head, 
shown  in  Fig.  E,  is  attached  by  means 
of  the  thumb-  nut  and  the  taper  end  at 
C  drops  into  this  screw-head,  turning  a 
vertical  into  a  horizontal  bearing,  the 
least  variation  in  the  location  of  the 
pivot-holes  in  the  "  lazy  tongs  "  or  pan- 
tograph will  be  met  by  an  absolute 
refusal  to  work  at  all,  and  we  have  no 
doubt  that  some  of  our  engineers  or 
mechanics  who  have  attempted  to  make 
a  pair  of  "  lazy  tongs,"  have  had  lots  of 
fun  out  of  it,  and  nobody  else  been  any  the  wiser  ;  whether  they  enjoyed  the 
fun  or  not,  we  do  not  know.  Correctly  made,  the  pantograph  is  complete,  but 
with  the  slightest  variation 
from  correct,  it  is  like  the 
diagram  from  a  distorted 
motion,  absolutely  incor- 
rect and  worthless. 

In  applying  the  panto- 


FIG.  J. 


graph,  let  the  end  C  drop 
into  any  point  on  the  cross- 
head  to  which  you  can  at- 
tach, or  any  one  of  many 
ways  which  will  readily 
suggest  themselves  to  the 
mechanical  engineer.  The 
end  D  may  drop  into  the  top  of  the  post,  or  we  frequently  build  ourselves  a 
little  stand  of  inch  boards,  four  inches  wide,  braced,  and  then  get  two  or 
three  hundred  pounds  of  old  iron  or  anything  else  which  is  heavy,  and  when 


FIG. 


TWENTY  YEARS   WI2H  THE  INDICATOR.  15 

we  get  it  in  line,  weight  it  down,  square  it,  have  the  points  C  and  D  exactly 
level  so  there  will  be  no  weave  or  strain,  or  cross  motion  which  will  vitiate 
the  correctness  of  your  diagram.  The  line  from  C  to  D  must  invariably 
be  at  right  angles  to  the  line  of  motion  of  the  cross-head,  and  absolutely  in 
the  center  of  motion ;  then  shove  your  post  at  D  out  or  in  to  get  more  or  less 
motion ;  put  the  stake-pin  F  wherever  you  want  it,  and  set  this  peg  F  so  that 
the  line  from  that  to  the  indicator  shall  be  parallel  to  the  piston  or  parallel 
to  the  line  of  motion  of  the  cross-head.  If  you  cannot  do  this,  or  if  from 
any  cause  it  is  necessary  to  have  the  peg-pin,  hitch-pin  or  stake-pin,  F, 
further  away  from  the  cylinder  than  the  indicator  connections  are,  imme- 
diately set  up  a  second  little  stand,  and  take  the  cord  from  the  peg  F 
parallel  to  the  motion  of  the  piston  and  around  the  guide  pulley  to  the 
indicator.  Whenever  the  pantograph  is  properly  put  up,  every  point  on  a 
line  from  C  to  D  is  a  positively  true  motion,  parallel  with  the  guides,  varying 
from  nothing  at  D  to  length  of  the  stroke  at  C.  Wherever  engineers  wish 
to  use  one  motion  for  several  engines  there  is  nothing  better  than  a  piece 
of  gas-pipe,  ground  off,  with  an  attachment  which  may  be  fastened  with 
a  set-screw  to  slide  up  or  down  to  fit  different  engines ;  to  this  at- 
tachment may  be  fastened  a  socket  to  catch  the  D  end  of  the  panto- 
graph while  the  other  catches  into  the  cross-head.  By  means  of  a  T  on  the 
top  of  the  piece  of  pipe,  which  has  a  flange  at  the  bottom  for  screwing  to  the 
floor,  are  connected  two  side  pipes  standing  at  a  right  angle  to  act  as  braces ; 
this  can  be  attached  to  any  engine  or  flange,  screwed  down,  the  braces  squared 
and  screwed  down,  the  piece  that  slides  up  or  down  put  at  the  proper  level, 
the  pantograph  hooked  on  and  you  are  all  ready  to  go  ahead. 

THE   AMERICAN   IDEAL   REDUCING   WHEEL 

A  more  recent  type  of  reducing  motion 
and  one  which  is  universally  used  is  the 
reducing  wheel. 

Figure  N  shows  the  Improved 
American  Ideal  Reducing  Wheel 
as  made  by  the  American  Steam  Gauge  & 
Valve  Manufacturing  Company.  It  is  adapted 
for  all  strokes  from  10"  to  72".     Aluminum 
FIG.  N  bushings  of  various  sizes  are  regularly  fur- 

nished for  strokes  from  18''  to  72".  The  spring  box  for  the  take-up  is  connected 
by  a  3  to  1  gear  with  the  cord  wheel  spindle.  The  cord  wheel  is  made  of 
aluminum  and  is  very  light,  being  fitted  with  a  steel  sleeve  to  resist  wear.  The 
pitch  of  the  thread  on  the  steel  screw  on  which  the  cord  wheel  rotates  is 
the  same  as  the  cord,  causing  the  same  to  wind  smoothly  on  the  surface  of 
the  wheel  and  to  pass  straight  over  the  pulley.  The  wheel  is  easily  attached 
to  the  indicator  direct,  or  may  be  placed  in  any  convenient  position  between 
the  indicator  and  crosshead.  It  is  sometimes  attached  to  the  engine  frame. 
The  cord  must  always  run  in  a  straight  line  and  passes  directly  from  the 


16  TWENTY  YEARS  WITH  THE  INDICATOR. 

indicator  around  the  aluminum  bushing  on  reducing  wheel,  which  must  be  of 
proper  size  for  the  stroke  used,  and  is  fastened  as  shown  in  cut.  The  tension 
of  the  spring  should  be  sufficient  to  keep  the  cord  taut  at  all  times.  To 
adjust  the  spring,  remove  screw  cap  which  holds  the  bushing  in  place,  and  raise 
the  spring  box  until  the  gears  disengage,  then  increase  or  lessen  the  tension  as 
desired.  A  greater  tension  than  is  required  only  increases  the  wear. 
Keep  the  wheel  well  oiled. 

SLIDING  LOOP. 

There  are  all  sorts  of  hooks,  slips,  knots,  and  other  matters  used  for 
connection ;  until  within  the  last  few  months  we  have  invariably  used  the  old- 
fashioned,  flat,  sliding  loop,  which  is  about  as  nearly  worthless  as 
anything  can  be.  While  doing  some  work  for  one  of  the  lines  of 
steamers,  our  attention  was  called  to  a  crude  idea  by  the  chief- 
engineer  of  one  of  the  ships  which  we  have  put  into  shape,  and 
is  shown  at  Fig.  L.  This  is  so  clearly  shown  that  no  descrip- 
tion is  necessary ;  it  is  a  piece  of  brass  tube,  spun  over  at  the  end, 
finished,  holes  bored  through  it  and  finished,  and  it  is  the  only 
thing  in  the  way  of  a  sliding  loop  we  have  ever  seen  yet  that  was 
worth  talking  about  or  using.  The  American  Steam  Gauge  Com- 
pany make  them,  there  is  no  patent  on  them,  and  any  one  has  the 
right  to  make  them.  We  prefer  always  to  use  a  plain  hook  on  the 
end  of  the  indicator  cord,  which  is  attached  to  the  paper  barrels, 
having  means  of  adjusting  by  use  of  this  sliding  loop  from 
FIG.  L.  large  to  small  or  long  to  short,  using  as  little  cord  as  possible, 
more  especially  on  a  high-speed  engine.  We  prefer  this  adjustment  to 
anything  we  have  ever  seen,  for  where  we  are  working  with  water  steam, 
more  or  less  heat,  oil,  or  any  of  the  other  accompaniments,  no  cord  will 
retain  its  position  for  any  great  length  of  time  by  any  device  we  have  ever 
used,  until  we  adopted  Fig.  L,  and  some  method  of  ready  adjustment  is  nec- 
essary. We  have  previously  referred  to  the  adjustment  of  the  paper  ban-el 
by  means  of  the  cord,  and  now  having  proceeded  to  obtain  the  diagram,  if 
the  directions  have  been  followed,  we  are  ready  to  commence  the  computation 
of  the  diagrams. 

THE  DIFFERENT  METHODS  OF  COMPUTING  THE  INDICATOR  DIAGRAM. 

The  indicator  Diagram,  having  been  taken,  should  bear  on  it  memoranda 
taken  with  each  and  every  diagram  when  it  conies  from  the  indicator,  wher- 
ever the  work  may  be  performed ;  this  data  should  bear  upon  each  diagram, 
or  each  pair,  the  diameter  of  the  cylinder,  the  length  of  stroke,  the  revolutions 
per  minute  and  the  scale  of  spring  with  which  it  is  taken,  for  these  are  the 
most  important  elements  and  without  them  the  diagram  cannot  be  correctly 
worked.  Wherever  it  is  possible  to  ascertain  the  percentage,  the  clearance 
should  also  be  noticed.  Many  engineers  of  late  have  accustomed  themselves 
to  ascertaining  the  clearance  of  their  engine  so  as  to  know  precisely  what  the 


TWENTY  YEARS  WITH  THE  INDICATOR.  17 

amount  is.  It  is  also  a  good  plan  to  carefully  note  the  pressure  of  steam  in 
the  boiler  by  the  gauge,  and  also  to  notice  whether  this  gauge  shall  be 
located  above  or  below  the  line  of  the  cylinder,  and  whether  there  is  hanging 
on  the  gauge  a  column  of  water  in  the  siphon  several  feet  in  length,  or  in  the 
vacuum  gauge,  how  or  where  it  is  connected,  for  we  frequently  find  very 
radical  differences  between  the  pressure  in  the  cylinder  and  the  pressure  as 
shown  by  the  gauge.  All  these  items  of  data  are  particularly  necessary,  for 
if  they  are  clearly  expressed,  we  may  then  judge  pretty  well  of  various 
peculiar  points  which  so  frequently  occur  on  the  diagram,  and  having  the 
data  at  hand,  we  can  in  every  case  base  our  judgment  upon  fact,  and  know 
how  a  certain  falling  off  or  back  pressure  or  any  peculiarities  of  steam  or  ex- 
haust will  be  explained  by  comparison  of  the  data  with  the  fact. 

WORKING  UP  THE  DIAGRAM. 

If  the  motion  has  been  properly  attached  to  reduce  the  stroke  of  the 
engine,  we  shall  have  an  accurate  card,  and  without  it  is  accurate,  it  is  not 
only  valueless  but  a  waste  of  time.  Endeavor  by  all  means  to  keep  the  card 
clean  and  to  avoid  the  possibility  of  any  mistakes.  The  general  unit  called 
for  is  the  horse-power  of  a  diagram ;  the  unit  of  horse-power  is  33,000  pounds 
lifted  one  foot  high  in  one  minute.  For  this  reason  we  use  the  length  of  the 
stroke,  the  revolutions  per  minute  and  the  mean  pressure  of  the  diagram,  and 
then  by  computation,  obtain  the  horse-power.  Having  our  diagram  before  us 
we  proceed  to  work  it  up,  and  the  working  up  simply  obtains  the  mean 
pressure  from  an  irregular  form.  There  are  several  ways  of  working  up  an 
indicator  diagram ;  the  one  most  generally  in  use,  up  to  five  years  ago,  was 
dividing  the  diagram  into  ten  ordinates  or  lines  at  right  angles  with  the 
atmospheric  line,  and  at  equal  distances  from  each  other,  and  then  measuring 
by  the  same  scale  with  which  the  diagram  was  taken,  the  pounds  of  pressure 
upon  each  one  of  these  ordinates,  which  was  exerted  on  the  piston,  then 
dividing  the  aggregate  by  the  number  of  amounts,  giving  the  average  or  mean 
pressure.  But  this  was  crude,  it  did  not  take  into  account  little  differences 
which  exist,  and  while  not  very  far  from  correct,  it  was  far  enough  to  make  a 
very  considerable  difference  as  between  the  correct  computation  and  the  one 
practiced ;  hence,  this  has  been  discarded  for  general  use. 

Another  way,  which  is  virtually  the  same  thing,  was  to  take  a  narrow 
strip  of  paper,  perhaps  one-eighth  or  one-quarter  of  an  inch  wide,  and  mark- 
ing the  steam  pressure  on  the  first  ordinate  from  the  end  of  the  paper  laid  on 
the  atmospheric  line  or  line  of  back  pressure,  then  put  the  first  mark  on 
the  atmospheric  line  or  line  of  back  pressure  of  the  second  ordinate,  and 
mark  the  top  of  the  second  ordinate  by  another  short  mark  of  the  lead  pencil ; 
in  this  way  we  are  simply  adding  them  together.  When  all  the  ordinates  have 
been  measured  (measure  them  in  inches),  multiply  by  the  scale  of  the  spring 
as  20,  30,  40,  and  divide  by  the  total  number  of  ordinates  measured,  and  you 
have  the  mean  pressure.  But  this  has  virtually  the  same  inaccuracies  as 
the  first  method  of.  measuring. 


18  TWENTY  YEARS  WITH  THE  INDICATOR. 

There  is  still  another  way  by  which  many  diagrams  have  been  measured, 
and  that  is  a  sort  of  general  average  ;  taking  a  piece  of  glass  with  a  straight 
edge,  it  is  placed  below  the  steam  line  and  above  the  lower  part  of  the  ex- 
pansion line,  until  the  two  quantities  apparently  balance  each  other  and  a  line 
drawn  across  the  length  of  the  diagram ;  its  height  found,  multiply  by  the 
scale,  this  gives  the  mean  pressure.  But  this,  too,  has  been  discarded  and 
for  the  last  few  years  the  planimeter  has  been  used,  and  is  the  only  correct 
way  to  work  up  any  diagram ;  the  fact  that  it  is  named  planimeter  is  another 
way  of  expressing  the  fact  that  it  is  for  measuring  plane  surfaces  without 
regard  to  how  irregular  their  form  may  be.  • 

Fig.  M  shows  a  modification  of  the  Amsler  Polar  Planimeter,  as  made  by 
the  American  Steam  Gauge  Company,  Boston.  Other  forms  of  the  instru- 
ment may  be  bought  if  desired.  The  proper  use 
of  the  planimeter  will  reduce  any  irregular  surface 
to  a  parallelogram  or  square  by  observing  its  reading 
carefully,  measuring  by  means  of  the  pointer,  and 
then  reading  from  the  index  wheel  and  vernier  and 
obtaining  the  value  as  indicated  by  simply  adding  or 
subtracting.  The  point  at  the  left  is  a  needle  point, 
which  should  simply  be  set  into  the  paper  on  which 
it  is  used,  and  it  is  better  to  use  a  medium,  rough, 
brown  paper  or  blotting  paper,  something  which  is 
not  calender  finished  on  the  surface,  than  to  use  a 
smoother  paper.  Having  fastened  the  card,  as  shown 
FIG.  M.  ^  ^6  cu^  by  a  COUpie  Of  pmg  or  tacks,  commence 

at  any  point  you  choose,  simply  making  a  mark  with  the  point  of  a  pencil ; 
traverse  the  point,  shown  at  the  right,  over  the  line  of  the  diagram  in  the 
direction  of  the  hands  of  a  watch,  or  from  right  to  left  on  the  line  which  is 
shown.  Having  pinned  the  diagram  down  on  the  paper  (which,  by  the  way, 
should  be  upon  a  smooth  board  or  surface),  next  adjust  the  planimeter  so  that 
the  index  wheel,  which  is  graduated  about  its  entire  circumference,  shall  not 
meet  with  any  obstacle  in  its  course,  or  anything  to  interfere  with  a  perfectly 
free  motion.  Now  obtain  the  reading.  There  are  a  series  of  figures  about 
the  circumference  of  the  index  wheel,  from  one  to  zero,  making  ten  lines ; 
each  one  of  these  divisions  has  ten  subdivisions,  while  the  vernier,  shown  at 
the  left  of  the  index  wheel,  has  eleven  divisions  in  exactly  the  same  distance 
that  the  large  wheel  has  ten,  so  that  wherever  the  index  wheel  stops  one 
division  on  the  vernier  will  be  bound  to  correspond  with  a  division  on  the 
index  wheel.  We  will  suppose  we  start  our  reading  and  that  the  figure  3  is 
past  the  zero  on  the  vernier ;  we  then  count  that  6  above  3  is  a  trifle  below 
zero  on  the  vernier.  We  now  cross  over  on  to  the  vernier  and  find  that  3  on 
the  vernier  exactly  coincides  with  a  division  on  the  wheel.  This  makes  GUI 
reading  363.  We  now  travel  the  index  point  at  the  right,  around  the 
diagram,  until  we  stop  at  the  same  point  from  which  we  started.  We  now 
find  that  5  has  passed  below  zero  on  the  vernier,  and  that  the  third  line  above 
5  has  also  passed ;  then  running  up  the  vernier,  we  find  that  8  stands  exactly 


TWENTY  YEARS  WITH  THE  INDICATOR.  li) 

coincident  with  a  line  on  the  index  wheel.  We  have  our  reading  then  538  ; 
subtract  the  first  reading  from  this,  the  result  is  175.  Now  repeat  the  opera- 
tion two  or  three  times  until  you  get  three  readings,  which  rnay  be  175,  176, 
174 ;  they  will  vary  exceedingly  little  if  you  pay  careful  attention  to  following 
the  lines.  The  average  of  these  three  readings  is  175,  which  is  correct. 
There  is  no  necessity,  although  it  sometimes  saves  trouble  with  a  beginner, 
or  doubter,  to  place  the  zero  on  the  wheel  against  the  zero  of  the  vernier  in 
starting.  If  this  precaution  is  considered  necessary,  a  few  trials,  without  com- 
mencing every  time  at  zero,  will  convince  any  one  that  it  is  entirely  unnecessary. 
We  first  read  from  the  index  wheel  the  figure  which  has  passed  the  zero  on  the 
vernier ;  this  we  will  call  hundreds.  Then  count  the  lines  up  until  you  find 
which  one  has  passed  zero  between  that  and  the  next  figure ;  this  is  tens. 
Then  follow  the  vernier  until  a  line  is  found  which  precisely  coincides  with  a 
line  on  the  wheel ;  this  is  units.  The  instrument  is  exceedingly  simple,  and 
there  can  be  no  mistake  whatever  if  care  is  given,  for  the  reading  is  just  like 
that  of  a  clock  or  watch — may  be  taken  at  any  point  through  the  day  without 
figuring  from  twelve  o'clock  or  six  o'clock.  This  gives  you  the  area  of  the 
figure  in  square  inches  or  in  fractions  of  a  square  inch.  In  case  you  read  so 
that  zero  on  the  wheel  completes  the  circuit  and  passes  zero  on  the  vernier, 
you  must  then  prefix  1  to  the  hightest  number  previously  read.  If  in  the 
case  we  have  just  cited  we  are  working  on  hundreds,  your  first  reading  should 
be  175,  the  second  350,  and  so  on  until  zero  passes;  you  would  then  prefix  1, 
which  would  make  it  thousands  instead  of  hundreds,  and  if  it  passes  again  it 
becomes  two  thousands  instead  of  one.  A  little  practice  with  the  instrument 
will  familiarize  any  one,  and  a  little  pains  taken  to  familiarize  yourself 
with  the  reading  will  shortly  put  you  in  possession  of  the  key  to  it,  all  which 
is  so  plain  that  no  mistake  need  occur.  The  instrument  will  work  precisely 
as  well  backward,  but  unless  care  is  taken,  and  you  should  obtain  a  diagram 
which  had  a  compression  loop  at  the  top  and  an  expansion  loop  at  the 
bottom,  you  might  get  a  negative  result  which  would  be  incorrect.  So,  until 
you  are  familiar  with  it,  always  work  it  like  the  hands  of  a  watch  or  as  shown 
in  the  cut,  from  right  to  letft,  following  the  diagram  around  in  the  same 
direction ;  there  will  then  be  no  possibility  of  trouble.  The  planimeter  does 
not  make  any  allowance,  but  if  the  work  is  correctly  done  you  have  at  once  a 
correct  result  from  the  outline,  and  by  the  use  of  the  planimeter  the  different 
areas  of  the  diagram  may  be  separately  measured  with  perfect  exactness,  so 
as  to  ascertain  the  value  of  the  vacuum  apart  from  the  steam,  or  the  high 
pressure  and  low  pressure  cylinders  of  the  compound  can  be  very  accurately 
measured,  without  any  regard  as  to  whether  they  are  all  taken  on  the  same 
scale  or  not. 

Another  point  which  is  frequently  one  of  great  interest,  is  to  measure  the 
difference  between  the  power  in  the  condenser,  taking  the  vacuum  gauge,  and 
the  result  as  given  by  the  indicator  in  the  condenser.  The  line  can  be  drawn 
to  show  what  would  be  the  result  in  case  the  pressure — as  shown  by  the 
vacuum  gauge — was  realized  in  the  cylinder ;  so  you  may  get  the  actual  as 
compared  with  the  gauge  result,  and  in  this  way  make  comparisons  showing 
the  absolute  value  of  any  factor  which  is  contained  in  the  diagram. 


20  TWENTY  YEARS  WITH  THE  INDICA  TOE. 


TO  ASCERTAIN  THE  POWER  FROM  THE  PLANIMETER  READING. 

Many  of  the  diagrams  illustrated  in  this  work  have  lines  at  the  steam  end, 
and  release  end,  which  are  erected  at  right  angles  to  the  atmospheric  line  and 
line  of  vacuum.  The  length  of  the  diagram,  without  any  regard  to  its  form, 
whether  there  be  a  heavy  compression  loop  on  the  steam  end,  or  an  expansion 
loop  on  the  other,  or  any  imperfection  in  release  or  exhaust, — the  length  of 
the  diagram  is  the  extreme  distance  from  the  very  ends,  and  if  a  little  attention 
is  paid  to  the  way  these  lines  are  erected,  there  will  be  no  necessity  for  any 
difficulty  in  getting  at  the  exact  area;  for,  wherever  a  compression  or 
expansion  loop  is  contained  in  the  diagram,  start  at  any  certain  point  and 
follow  the  diagram  line  as  the  indicator  made  it,  and  the  loops,  which  are 
resistance,  will  be  taken  out  of  the  area  by  the  instrument  without  any  further 
care  on  the  part  of  the  manipulator. 

Having  accomplished  the  measurement  of  the  area,  we  now  desire  to 
compute  the  power.  In  order  to  save  a  great  many  figures  it  is  better  to 
compute  a  constant  for  each  pound  of  mean  pressure  (even  if  at  different 
speeds)  instead  of  having  to  do  this  with  every  diagram  which  is  worked  up. 
This  is  produced  as  follows :  Take  the  area  of  the  piston  in  square  inches, 
multiply  this  by  the  number  of  feet  traveled  each  minute,  and  divide  this  re- 
sult by  33,000;  the  result  will  be  the  constant  which  shows  how  many  horse- 
powers, or  what  fraction  of  a  horse-power,  is  yielded  by  every  pound  of  mean 
pressure  on  the  diagram.  Having  the  area  of  the  diagram  in  square  inches 
or  fractions  of  an  inch,  divide  the  area  by  the  length  in  inches  or  fractions 
of  an  inch  (farther  on  in  this  work  will  be  found  a  table  of  fractions 
of  an  inch,  decimally  expressed,  for  convenient  reference), — the  area  divided 
by  the  length  of  the  diagram  gives  a  result  which  may  be  a  decimal  or 
otherwise.  This  is  to  be  multiplied  by  the  scale  of  the  spring  for  the  mean 
pressure ;  then  the  mean  pressure  multiplied  by  the  constant  (directions  for 
which  are  given  above)  gives  us  at  once  the  horse-power,  and  in  the  simplest 
possible  way. 

If  we  have,  for  instance,  a  diagram  measuring  450,  which  is  equal  to  4.50 
square  inches,  and  which  is  2T^  inches  in  length,  see  the  table  and  find  that 
T\  equals  .4375  inch.  Now,  the  area  4.50,  divided  by  2.4375,  equals  1.846, 
which  means  that  a  parallelogram  1.846  inch  in  height  would  be  exactly 
equal  to  the  irregular  figure  which  has  been  described  by  the  indicator.  If 
we  have  been  working  with  a  30  scale  we  have  only  to  multiply  this  1.846 
inch  by  the  scale  30,  which  equals  55.380  pounds  of  mean  pressure;  multiply 
this  by  the  constant  or  number  of  horse-powers  which  every  pound  of  mean 
pressure  gives,  and  you  have  then  the  horse-power  of  the  diagram. 

It  is  frequently  a  matter  of  satisfaction  to  the  beginner,  in  the  use  of  the 
planimeter,  to  have  something  with  which  to  test.  This  can  be  very  easily 
arranged  by  drawing  a  circle  with  a  pair  of  pen  dividers,  one  inch  in  diameter, 
or  any  other  sized  circle  that  may  be  desired  (we  mention  the  circle  because 


TWENTY  YEARS  WITH  THE  INDICATOR.  21 

it  is  more  easily  drawn  correctly,  as  a  general  thing).  Having  this,  measure 
it  by  the  planimeter  and  then  see  if  its  reading  agrees  with  the  table  of  areas. 
This  will  always  give  you  a  test  gauge. 


DIFFERENT  FACTORS  IN  THE  DIAGRAM. 

It  is  frequently  necessary  to  ascertain  the  amount  of  bank  pressure  in 
horse-power,  which  can  be  done  if  the  atmospheric  line  is  perfectly  taken 
and  the  diagram  is  also  correct.  The  amount  of  vacuum  in  comparison  with 
the  amount  of  steam  worked,  or  the'loss  in  vacuum — all  of  these  are  interest- 
ing features ;  while  if  the  reader  will  familiarize  himself  with  the  theoretical 
curve,  as  applied  to  any  diagram  shown  in  the  lessons  further  on  in  the  work, 
he  can  then  see  what  amount  of  steam,  properly  handled,  would  have  done 
the  same  or  more  work,  perhaps,  than  is  shown  by  the  diagram  from  which  he 
is  working.  The  planimeter  is  invaluable  for  all  this.  To  get  the  percent- 
age of  the  condenser  work,  as  approximating  the  theoretical,  erect  the 
absolute  vacuum  line,  and  then  measure  the  exact  amount  of  vacuum  as  shown 
by  the  indicator,  and  it  is  very  easy  to  immediately  convert  the  actual  into  a 
percentage  of  the  theoretical,  taking  the  theoretical  vacuum  at  14.7  pounds. 
Comparison  of  realized  pressure  with  boiler  pressure  is  frequently  an  inter- 
esting matter.  Erect  the  line  of  boiler  pressure,  from  which  you  can  carry 
all  computation,  so  as  to  get  at  the  actual  and  the  theoretical.  The  plan- 
imeter measures  these  irregular  forms  with  absolute  correctness,  if  the  operator 
works  with  care  in  tracing  the  lines,  and  in  a  fraction  of  the  time  that  would 
be  necessary  by  any  other  method. 


NECESSITY  OF  RELIABLE  DATA. 

There  is  frequently  a  great  deal  of  ambiguity  about  information  obtained 
from  people  in  charge  of  different  engines.  Wherever  a  man  is  sent  to  work 
with  an  indicator,  there  is  only  one  correct  way :  Pull  off  the  cylinder  head, 
measure  the  cylinders  and  the  volume  of  clearance,  and  make  everything  as 
near  correct  as  possible,  for  very  slight  differences  are  frequently  fatal  to  the 
report  on  the  case,  and  carelessness  is  entirely  inexcusable,  guess-work  or 
assumption  very  much  more  so,  and  we  have  seen  old  and  intelligent 
engineers  thrown  out  of  court  very  abruptly,  because  of  some  radical  error, 
even  though  trifling  in  extent,  shown  in  their  report,  where  they  had,  to  save 
themselves  a  few  hours'  hard  work,  assumed  that  because  one  part  was  one 
size,  the  other  was  the  other,  or  some  other  equally  trifling  matter  which  was 
more  than  vital  to  the  case.  While  some  more  careful  man  had  shown  in 
details  that  such  difference  existed,  and  by  that  means  had  thrown  doubt  on 
the  whole  of  the  work  of  the  careless  man.  Correctness  in  every  possible  way 
is  an  element  of  value,  and  a  lack  of  care  or  thoroughness  makes  an  indicator 
diagram  absolutely  worthless. 


22  TWENTY  YEARS    WITH  THE  INDICATOR. 


LESSON   I. 


BACON'S  METHOD  OF   LAYING  OUT  THE  THEORETICAL  CURVE  BY  ORDINATES. 

Fig.  6  was  drawn  by  Mr.  Bacon  to  illustrate  a  simple  and  correct  method 
of  delineating  the  theoretical  curve  of  expansion,  which  we  shall  take,  as  it  is 
properly  lettered,  upon  which  to  commence  our  lessons  in  the  general  uses  of 
the  different  lines,  and  this  will  be  frequently  referred  to ;  it  will  therefore  be 


Fio.6. 

well  for  the  beginner  to  familiarize  himself  with  reference  to  this  particular 
figure.  For  the  time  being  we  shall  confine  ourselves  to  the  outlines  bounded 
by  the  letters  A,  B,  C,  D,  E.  The  line  A  E  represents  the  true  vacuum  line ; 
the  line  A  B  the  admission  line ;  B  C  the  steam  line ;  C  D  the  line  of  expan- 
sion; D  E  A  the  exhaust  line,  and  as  this  engraving  is  made,  it  represents 
exhaust  and  vacuum  lines,  while  the  line  between  D  and  E  running  the  whole 
length  of  the  figure  and  seen  above  A,  between  A  and  B,  is  the  atmospheric 
line  of  the  instrument  or  of  a  high  pressure  engine  These,  in  brief,  are  the 
various  lines  of  any  high  or  low  pressure  engine.  No  matter  what  form  the 
diagram  may  take,  whether  it  be  a  finely  proportioned  one  or  one  that  may  be 
full  of  errors,  these  lines,  in  some  relative  proportion,  all  exist  in  every 
Indicator  diagram.  The  admission  line  in  this  case  is  very  nearly  perfect,  — 
in  fact,  too  nearly  perfect,  —  and  it  would  not  be  advisable  in  changing  the 


TWENTY  YEARS    WITH  THE  INDICATOR.  23 

valves  of  an  engine  to  ever  produce  an  absolute  right  angle  for  an  admission 
line,  except  in  a  very  slow  moving  and  low  pressure  engine;  for  in  a  high 
pressure,  fast  moving  engine,  there  would  be  a  certain  shock  by  the  production 
of  a  line  of  this  sort  on  the  Indicator,  and  it  is  much  better  to  confine  a  small 
amount  of  steam  by  shutting  the  exhaust  valve  so  as  to  put  in  compression  or 
cushioning.  This  would  be  done  by  shutting  the  exhaust  valve  between  the 
figure  i  and  A  on  the  vacuum  line,  so  that  the  line,  instead  of  starting  from  A 
to  go  to  B,  would  start  from  a  point  between  A  and  the  figure  i  and  gradually 
rise  one-quarter  or  one-third  of  the  distance  from  A  to  B.  The  line  of  which 
we  are  speaking  is  not  represented  in  the  engraving,  but  would  be  represented 
in  about  the  manner  we  have  described.  This  is  very  much  more  advisable  in 
fast  moving  engines,  from  the  fact  that  the  steam  thus  confined  costs  nothing, 
and  it  is  much  better  to  assist  the  piston  in  coming  to  a  stop  without  having  a 
tendency  to  go  any  further,  if  it  were  possible.  It  prevents  a  strain  upon  the 
connections  and  really  assists  the  whole  thing  to  come  to  a  stand-still  while  the 
crank  passes  the  absolute  center. 

As  we  progress  in  this  study  of  lines,  a  very  considerable  change  will  be 
observed  in  the  steam  line  as  well  as  in  the  admission  line.  Upon  this  point 
of  admission  line  a  great  many  good  engineers  run  away  with  the  theory  that 
they  can  tell  as  well  by  the  lead  of  the  valve,  as  by  the  Indicator,  what  the 
steam  line  of  an  engine  is.  It  is  just  as  well  to  disabuse  yourself  of  any 
preconceived  ideas,  for  they  are  simply  and  only  guesses,  and  no  living  man 
can  tell  anything  about  the  lines  made  by  the  action  of  the  steam  in  the 
cylinder,  by  any  marks,  figures/  or  computations,  and  only  until  he  applies 
the  Indicator,  does  he  know  anything  about  what  is  going  on.  He  can 
theorize  and  suppose,  but  it  is  simply  and  purely  theory  and  supposition. 
There  is  nothing  actual  or  absolute  about  it. 

We  now  come  to  the  steam  line,  B  C.  The  diagram  here  represented  is 
one  which  is  like  what  would  be  taken  from  an  automatic  cut-off  engine  in 
which  the  point  of  cut-off  is  controlled  by  the  action  of  the  governor,  either 
by  changes  in  the  pressure  of  steam  or  by  changes  in  the  load.  This  class  of 
diagrams  is  different  from  those  of  other  engines.  This  may  be  described  as 
admitting  the  full  pressure  of  steam  for  a  limited  amount  of  stroke,  —  the 
steam  is  then  cut  off  and  expansion  finishes  the  stroke.  The  other  classes,  or 
groups,  are  described  by  a  valve  having  an  invariable  motion,  but  with  more 
or  less  lap,  which  closes  the  valve  for  a  portion  of  the  stroke,  always  cutting  it 
off  at  a  certain  fixed  point,  the  pressure  being  changed  by  the  throttle -valve 
of  the  regulator. 

There  is  still  another  class,  which  is  virtually  a  subdivision  of  the  one  we 
have  last  mentioned,  in  which  the  motion  of  the  valve  may  be  changed  by 
hand,  either  by  link  motion  or  an  independent  cut-off  gear.  Both  of  these 
classes  use  a  regulator  in  the  pipe  which  governs  the  pressure  of  steam 
admitted  through  a  portion  of  the  stroke ;  that  portion  of  the  stroke  remains 


24  TWENTY  YEARS    WITH  THE  INDICATOR. 

constant  —  it  is  always  the  same.  This  is  the  case  in  the  Huntoon,  Judson, 
Waters,  and  many  other  governors  of  that  class,  which  regulate  by  means  of 
a  valve  in  the  steam -pipe,  governing  the  amount  of  steam  required  by  a  fixed 
motion  of  the  valve,  instead  of,  as  in  the  previous  case,  the  automatic  cut-off, 
like  the  Corliss,  Lawrence,  Porter-Allen,  and  others,  in  which  the  full  boiler 
pressure  is  admitted  for  a  length  of  the  stroke,  which  is  controlled  by  the 
governor. 

There  is  only  one  other  class  of  engines,  and  that  is  the  old  style  plain 
slide  valve  engine,  having  an  invariable  motion  without  lap  of  any  amount,  so 
that  the  steam  follows  the  piston  for  nearly  the  whole  length  of  the  stroke. 
In  some  cases,  the  mean  pressure  in  the  cylinder  is  adjusted  by  changing  the 
point  of  cut-off,  as  in  an  independent  cut-off  gear ;  but  these  engines  are  only 
applicable  to  work  in  which  there  is  very  little  or  no  variation  in  the  load,  and 
they  are  not  at  all  applicable  to  the  modern  system  of  working,  where  accuracy 
in  the  speed  is  one  of  the  important  requirements. 

In  the  consideration  of  these  various  classes  of  engines,  we  shall  first  look 
after  the  automatic  cut-off,  because  it  is  the  most  effective,  the  most  economi- 
cal, and  by  far  the  most  used.  Its  lines  are  always  defined.  They  may  or 
may  not  be  correct,  but  in  some  of  the  classes  to  which  we  have  referred,  it  is 
extremely  difficult  to  ascertain  where  one  of  the  lines  commences  or  another 
one  leaves  off. 

The  steam  line,  B  C,  is  one  of  the  important  lines  of  the  diagram.  It  is 
very  frequently  the  case  that  the  line,  B  C,  drops  away  from  C,  sometimes 
more,  and  sometimes  less.  The  engine  that  comes  nearest  to  good  prac- 
tice will  maintain  its  steam  line  as  nearly  as  possible  to  a  straight  line ;  and 
wherever  any  considerable  variation  is  found,  it  may  result  from  one  of  several 
causes — principally  two  causes;  the  first  may  be  an  insufficient  supply  from  the 
boilers  to  the  chest  of  the  engine  —  that  is,  the  steam  pipe  is  not  large  enough, 
or  the  valve  may  not  be  as  large  as  the  pipe ;  and,  in  the  other  case,  to  a  very 
late  and  incorrect  opening  of  the  steam  valve.  In  either  case,  the  lack  of  a 
good  steam  line  is  a  lack  of  economy.  The  opening  of  a  valve,  or  an  insuffi- 
cient area  in  the  ports,  may  also  combine  to  produce  an  imperfect,  throttled, 
or  wire-drawn  steam  line  upon  the  Indicator  diagram.  The  steam  line  should 
therefore  approach  closer  to  boiler  pressure,  and  should  be  as  nearly  as 
possible  at  right  angles  from  the  line,  A  B,  until  the  cut-off  valve  closes.  The 
piston,  in  traveling  from  B  to  C,  is  influenced  by  the  total  boiler  pressure. 
When  the  piston,  in  its  track,  reaches  the  point,  C,  the  steam  valve  is  closed. 
Now  commences  the  line  of  expansion.  The  perfection  of  this  .line  depends 
upon  various  and  important  causes.  The  cut-off  valve  should  close  instanta- 
neously ;  the  valve,  in  its  action,  should  work  quick,  or  else  we  shall  have  an 
exaggerated  expansion  line ;  because,  if  the  valve  works  slowly  or  imperfectly, 
it  will  commence  to  reduce  the  pressure,  and  will  still  be  admitting  steam,  so 
that  the  line  of  expansion  may  be  plus  at  one  point  and  minus  at  another, 


TWENTY  YEARS    WITH  THE  INDICATOR.  25 

when  proved  by  the  theoretical  curve.  Only  the  Indicator  can  tell  us  whether 
the  engine  is  constructed  properly,  or  with  a  capability  of  doing  this  properly 
and  correctly,  —  and  when  the  valve  closes  it  must  be  tight.  If  any  steam 
leaks,  or  is  drawn  under  the  valve  after  it  is  closed,  it  is  a  waste  of  steam,  and 
is  certainly  not  an  improvement  upon  the  working  of  the  engine.  But  these 
points  must  be  treated  upon  as  individual  cases  rather  than  as  collective  ones. 

We  now  come  to  the  consideration  of  the  line,  C  D,  —  which  is  the  curve 
formed  by  the  expansion  of  the  steam  from  a  higher  pressure  to  a  lower  one, 
by  increasing  the  room  in  the  cylinder,  by  the  motion  of  the  piston,  from  one 
end  to  the  other.  This  is  usually  known  as  Mariotte's  law :  that  the  pressure 
of  steam  diminishes  in  proportion  to  its  volume ;  in  other  words,  that  steam, 
at  100  pounds,  expanded  into  double  the  room,  would  give  a  pressure  of  50 
pounds ;  and  into  four  times  the  room,  25  pounds.  The  use  of  the  theoretic 
curve  is  a  very  considerable  and  valuable  one ;  but  only  as  a  means  of  com- 
parison, no  man  has  yet  shown  that  steam  does  expand  as  Mariotte  laid  down 
the  law  as  given.  By  its  proper  application  we  erect  a  theoretically  correct 
diagram,  —  in  other  words,  a  perfect  diagram.  Now,  the  line  of  the  perfect 
diagram,  if  properly  done,  with  the  proper  data,  shows  what  the  engine  should 
have  done  with  the  amount  of  steam  and  the  ratio  of  expansion,  as  applied  to 
that  individual  circumstance.  In  this  way  we  get  a  theoretical  diagram  erected 
from  the  data  of  the  actual  diagram,  and  we  can  then  ascertain  whether  the 
actual  diagram  is  a  large  or  small  percentage  of  the  theoretical.  The  curve 
erected  from  C  to  D,  illustrates  Mr.  Bacon's  method  of  easily  ascertaining  just 
what  the  theoretical  curve  should  be.  The  ordinates  are  here  erected,  making 
ten  spaces,  or  divisions ;  he  cuts  off  the  steam  at  the  second  ordinate.  If  the 
pressure  be  sixty  pounds  from  A  to  B,  and  be  maintained  from  B  to  C,  it  is 
cut  off  at  two  ordinates.  The  pressure  at  which  the  next  ordinate  should 
measure  is  two-thirds  its  former;  and  then,  as  will  be  seen  by  his  method, 
two-fourths,  two-fifths,  two-sixths,  two-sevenths,  two-eighths,  two-ninths,  two- 
tenths.  Theoretically,  this  is  correct.  If  the  curve  given  by  the  instrument 
should  be  above  the  theoretical  curve,  we  conclude  that  the  steam  valve  leaks. 
But  if  we  find  the  curve  made  by  the  Indicator  falling  below  the  theoretical 
line,  we  are  certain  that  either  the  piston  or  the  exhaust  valve  leaks,  or  that 
we  have  discovered  something  new,  —  which  is  not  likely,  however,  to  be  the 
case.  This  line  varies  greatly  in  different  engines. 

To  apply  the  theoretic  curve  to  any  diagram,  add  the  clearance  between 
the  piston  and  cover,  or  head  of  the  cylinder,  to  which  add  the  area  of  the 
ports  and  passage  ways  clear  to  the  face  of  the  valves ;  reduce  this  clearance 
to  cubic  inches,  then  ascertain  the  actual  number  of  cubic  inches  in  the  stroke 
of  the  cylinder,  and  get  the  percentage  or  proportion  of  clearance  to  the  vol- 
ume of  cylinder.  If  the  stroke  of  the  cylinder  has  two  thousand  inches,  and 
the  clearance  is  fifty  inches,  the  percentage  will  be  one-fortieth,  or  two  and 
one-half  per  cent. ;  now  add  one-fortieth  to  the  length  of  your  diagram,  then 


26 


TWENTY   YEARS    WITH  THE  INDICATOR. 


draw  the  line  of  perfect  vacuum,  from  which  all  the  calculations  must  be  made. 
Whether  the  engine  is  high  or  low  pressure  makes  no  difference.  Having 
added  the  clearance  line,  and  the  line  of  perfect  vacuum,  then  divide  the 
length  of  the  diagram  into  ten  parts,  or  spaces.  If  the  steam  is  expanded, 
four  times  the  terminal  pressure  will  be  one-fifth  of  the  initial.  This  will  be 
above  the  atmospheric  line  of  the  instrument — not  above  the  true  vacuum  line. 


LESSON   II. 


IN  this  lesson  two  diagrams  are  shown,  which  are  as  radically  different  as 
is  possible,  in  the  action  of  the  valves  and  the  steam,  so  far  as  principle  is  con- 
cerned. In  reading  these  diagrams,  it  is  necessary  to  remember  one  point,  to 
which  we  have  previously  referred;  that  is,  that  the  Indicator,  when  properly 


applied,  records  absolutely  the  performance  that  is  going  on  inside  the 
cylinder.  We  must  educate  ourselves  to  read  these  lines  properly  and 
correctly.  The  Indicator  is  simply  a  mechanical  appliance.  It  does  not.  in 
any  event,  do  anything  more  than  record  the  processes  which  are  taking  place 
inside  the  cylinder.  We  must  properly  apply  and  manipulate  it,  and  then 
draw  our  deductions  from  its  lines,  from  knowledge  gathered  from  experience 
and  contact  with  it. 

Fig.  7  is  a  diagram  taken  from  a  Corliss  engine.  The  real  vacuum  line 
has  been  drawn,  while  the  atmospheric  line  extends  from  O,  on  the  right,  to  A, 
on  the  left.  Two  lines  are  erected,  one  of  which  is  the  right  angle  from  which 


TWENTY   YEARS    WITH  THE  INDICATOR.  27 

to  measure  the  length  of  the  diagram ;  and  the  line  at  the  extreme  right  is  the 
clearance  of  the  engine,  added  for  the  purpose  of  putting  in  the  expansion  or 
theoretical  curve,  which  is  shown  by  the  dotted  line.  This  diagram,  in  itself, 
is  quite  a  study.  Theoretically,  it  is  almost  absolutely  perfect.  Four  motions 
of  the  piston  are  recorded  by  the  pencil  mark  of  the  Indicator,  and  if  careful 
attention  is  given  to  the  dotted  line,  it  will  be  seen  that  the  valves  of  the  engine 
were  almost  absolutely  tight ;  that  very  little  condensation  took  place,  and  that 
the  termination  of  the  correct  expansion  curve  at  A,  is  as  nearly  correct  as  it 
is  possible  in  actual  practice  to  obtain  one.  This  diagram  is  divided  in  two 
directions  —  the  lines  from  right  to  left  being  at  five  pounds,  with  the  scale 
used,  so  that  the  pressure  at  any  point  upon  the  diagram  can  be  shown  without 
using  the  scale.  The  ordinarily  used  ordinates,  and  the  clearance  line  erected, 
complete  the  lines  of  the  figure.  If  we  study  the  lines  near  the  upper  right 
hand  corner,  the  line  drawn  by  the  pencil  of  the  Indicator  is  at  a  little  distance 
from  the  inner  line  of  ordinates.  A  little  space  will  be  seen  between  the  inner 
line  and  the  steam  line  near  the  figure  75.  Whatever  proportion  this  distance 
shall  bear  to  the  whole  length  of  the  diagram,  just  that  proportion  of  the 
stroke  the  piston  had  moved  on  its  outward  travel  before  the  valve  opened 
sufficiently  to  admit  the  steam  to  the  pressure  denoted  by  the  line.  In  other 
words,  steam  was  admitted  somewhat  late.  This  is  a  very  common  observa- 
tion where  engines  have  been  running  any  length  of  time.  The  steam -line  of 
this  engine,  as  we  have  before  stated,  is  almost  perfection.  It  does  not 
diminish  in  pressure,  but  follows  along  very  squarely,  and  wherever  the  valve 
closes,  or  cuts  off,  the  pressure  instantly  drops,  the  corners  are  very  little 
rounded,  and  in  the  expansion  line  it  will  be  seen  that  very  little  expansion 
occurs.  The  serrations  in  the  line  at  the  second  ordinate,  between  the  figures 
40  and  67,  may  be  made  by  either  one  of  several  causes ;  it  may  be  due  to  a 
trifling  oscillation  in  the  instrument,  to  the  presence  of  water,  or  to  a  very 
insignificant  leak;  we  are  supposing  the  instrument  is  in  perfect  order  and 
condition.  As  the  ratio  of  expansion  increases,  the  line  more  closely  follows 
the  theoretical  line,  and  it  will  be  noticed  that  the  four  lines  are  all  merged 
into  and  apparently  cross  one  another  at  almost  the  same  precise  spot.  Had 
the  steam  valve  been  leaking,  or  had  there  been  much  water  in  the  steam,  the 
line  under  the  figure  7^  would  have  risen  considerably  above  the  theoretical 
line,  —  and  this  is  very  commonly  found,  —  but  in  this  particular  case  the 
valves  were  tight,  and  the  line  continues  down  to  its  complete  expansion,  or 
termination,  almost  absolutely. 

Fig.  8  is  a  very  different  diagram,  and  was  taken  from  a  steamship  engine ; 
and  this  may  properly  be  termed  one  of  the  vicious  forms,  or  at  least  a  vicious 
diagram ;  and  even  now,  we  find  some  men  so  antiquated  as  to  advocate  this 
method  of  working  steam.  It  must  be  read,  not  from  its  comparison  with  the 
other,  so  far  as  the  Indicator  goes,  but  as  an  absolute  result  given  by  the  Indi- 
cator of  what  was  being  done  in  that  engine  at  that  time,  and  we  can  then 


28  TWENTY  YEARS    WITH  THE  INDICATOR. 

compare  it  with  Fig.  7,  each  diagram  being  the  positive  production  of  a  differ- 
ent engine,  given  by  the  same  Indicator,  perhaps,  just  the  same  as  a  pair  of 
scales  would  weigh  a  pound  of  sugar  or  a  pound  of  nails.  The  work  done 
by  the  scales  is  simply  a  mechanical  result,  while  the  matter,  which  passes  the 
hands  of  the  operator  of  the  scales,  may  be  as  entirely  dissimilar  as  sugar  and 
nails.  This  diagram  has  in  it  some  very  peculiar  points. 


Fig.  8  is  taken  upon  a  scale  of  twelve  pounds  to  the  inch.  The  line, 
A  O  B,  is  the  atmospheric  line,  while  the  line,  C  D,  is  the  line  of  perfect 
vacuum.  We  have  previously  spoken  of  compression.  It  is  illustrated  in 
this  diagram,  and  we  shall  commence  at  /,  in  the  right  hand  corner,  where  the 
piston,  on  its  return  stroke,  in  passing  /",  commences  to  compress  the  steam 
which  the  closing  of  the  exhaust  valve  has  confined.  The  operation  in  this 
case  would  seem  to  reach  about  five  pounds  above  the  atmospheric  line ;  at  a, 
the  steam -valve  has  opened,  and  the  steam  is  admitted,  carrying  the  pressure  up 
to  b.  Then  the  piston  starts  upon  its  forward  stroke.  The  continued  opening 
of  the  valve  maintains  the  pressure  at  almost  the  initial  point.  When  the 
piston  has  traveled  forward  to  c,  the  steam -valve  commences  to  close,  and 
continues  to  close,  but  the  actual  point  of  closing  cannot  be  ascertained  from 
the  diagram  without  geometrical  delineation ;  but  had  the  valve  been  properly 
closed  at  c, — as  it  should  have  done  with  an  automatic  engine, — then  the  dotted 
line,  eg,  would  have  been  approximated  very  nearly  by  the  steam -line,  the 
lines,  eg,  being  the  theoretical  expansion  curve  from  the  point,  c,  and  the  line, 
£  dy  the  real  expansion  curve  of  the  engine.  At  d  the  exhaust  valve  com- 


TWENTY   YEARS    WITH  7^HE  INDICATOR.  29 

mences  to  open  and  the  condenser  to  do  its  work  in  producing  a  vacuum. 
The  vacuum  in  this  case  is  about  twelve  pounds.  The  notch  in  the  line, 
between  e  and/,  is  caused  by  the  fact  that  the  air  was  expelled,  or  that  the 
condenser  had  then  produced  its  maximum  effect.  The  line  here,  <?/  will  be 
seen  to  drop  from  9  below  to  12+.  When  the  condenser  takes  hold  at  d,  the 
steam  has  expanded  to  only  two  pounds  above  the  atmospheric  line,  the 
piston  has  not  reached  the  full  length  of  its  travel,  and  the  condenser  seems 
not  to  have  the  capacity  to  take  and  produce  a  prompt  vacuum.  When  the 
engine  reaches  its  center,  on  the  outward  stroke,  it  will  be  seen  at  q  that  the 
line  of  the  instrument  drops  vertically.  At  e,  the  piston  has  commenced  its 
return  stroke.  Only  nine  pounds  vacuum  has  yet  been  attained.  As  the 
piston  travels  on  its  return  stroke,  the  condenser  commenced  moving  again, 
and  the  vacuum  is  steadily  reduced  from  9  to  12  in  about  one-seventh  of  the 
return  stroke. 

We  are  now  to  return  to  the  expansion  curve,  real  and  theoretical.  The 
area  bounded  by  the  line,  c  d g,  and  eg,  is  really  just  the  same  as  so  much 
steam  thrown  away ;  for,  had  the  valve  closed  at  c,  the  line,  c  g,  would  have 
been  produced ;  but  as  the  valve  was  so  slow  in  its  closing,  the  quantity  of 
steam  admitted  led  the  real  line  of  expansion  unusually  far  above  the  theoret- 
ical ;  and  while  a  certain  amount  of  power  was  produced,  it  was  at  an 
enormous  expense  compared  with  the  rest  of  the  area  of  this  diagram,  —  really 
at  no  positive  advantage. 

In  comparing  the  two  diagrams,  Fig.  7  shows  the  perfection  of  the 
working  of  steam,  and  Fig.  8,  we  might  with  propriety  say,  the  perfection  of 
waste  of  steam.  Although  the  one  is  called  a  high,  and  the  other  a  low 
pressure  diagram,  had  a  condenser  been  attached  to  the  engine  from  which 
Fig.  7  was  taken,  there  would  not  have  been  the  least  difficulty  in  producing  a 
better  vacuum  than  that  of  Fig.  8,  and  the  waste  between  the  two  engines 
would  be  enormous  if  they  were  both  adapted  to  the  same  work. 

We  shall,  in  another  lesson,  show  a  diagram  from  a  modern  steamship 
engine,  which  is  as  radically  different  from  Fig.  8,  as  Fig.  8  is  different  from 
Fig.  7.  The  figures  upon  these  diagrams  are  the  old  method  of  working  up, 
and  it  will  be  good  practice  to  work  these  over  and  corroborate  the  figures, 
or  to  make  a  nice  tracing  of  these  diagrams,  lay  out  the  curves,  and  find  the 
percentages  of  economy  and  waste. 

There  are  high  pressure  engines,  now  running,  which  are  fully  as  wasteful 
as  Fig.  8,  some  of  which  we  shall  illustrate ;  but  it  must  be  borne  in  mind  that 
this  diagram  was  taken  a  number  of  years  since,  when  it  was  supposed  a  great 
improvement  had  been  made  in  working  steam  expansively  upon  marine 
engines.  Many  marine  engines  have  most  elegantly-contrived  expansion 
valves,  or  arrangements,  which  we  shall  treat  upon  more  fully.  Fifteen  years 
ago  it  was  supposed  that  some  of  the  steamships  crossing  the  Atlantic  had 
reached  the  highest  point  in  the  economy  of  fuel ;  but,  within  the  last  eighteen 


30  TWENTY  YEARS    WITH  THE  INDICATOR. 

months,  vessels,  with  more  tonnage  than  those  with  which  the  comparison  was 
made,  have  crossed,  from  New  York  to  Liverpool,  upon  a  little  less  than  one- 
fourth  the  amount  of  fuel  per  day  than  the  engines  are  using  which  were  sup- 
posed to  be  so  economical;  while,  in  other  departments  of  working  steam, 
results  have  been  obtained,  by  the  application  of  steam  pumping  of  water, 
which  far  surpass  the  performance  of  any  steamship  engine  that  has  been  built 
up  to  this  date.  This  has  been  done,  partially,  by  studying  carefully  the 
force,  and  its  application  to  raising  water ;  but  if  the  steam  mechanism  had 
not  been  as  nearly  perfect  as  it  is  possible  to  make  it,  it  would  not  have  shown 
such  immensely  economic  results.  The  perfection  of  application  of  the  power 
produced  has  wrought  out  this  result  —  to  which  we  shall  again  refer. 

The  study  of  this  diagram,  by  those  who  are  not  entirely  familiar  with  the 
Indicator,  will  be  of  great  value.  No  man  should  be  intrusted  with  the  run- 
ning of  large  engines,  especially  in  cotton  or  woolen  mills,  where  perfection  of 
speed  is  required,  and  where  the  best  results  that  are  possible  are  not  only 
desirable  but,  from  an  economic  point  of  view,  are  a  most  imperative  necessity. 
Many  of  our  larger  corporations  now  require  that  an  engineer  shall  have  a 
practical  knowledge  of  the  Indicator  before  they  will  put  him  in  charge  of 
their  engines  and  boilers.  The  time  for  setting  the  valves  of  an  engine  by  the 
eye,  or  by  scratches  or  punch  marks,  has  ceased  to  exist  in  the  eyes  of  intelli- 
gent and  competent  engineers ;  and  the  engineer  of  the  future  is  probably  a 
man  who  is  capable  of  a  careful  manipulation  of  the  Indicator,  and  of  producing 
the  highest  economic  results  from  following  the  lines  drawn  therefrom,  without 
regard  to  the  whims  of  the  builder,  owner,  or  others,  after  he  has  qualified 
himself  to  read  these  lines,  and  make  them  by  the  proper  manipulation  of  his 
instrument. 


LESSON   III. 


IN  this  lesson  we  present  two  diagrams  from  different  classes  of  valve 
motions,  and  the  two  figures  represent  as  radical  a  difference  as  is  possible, 
from  the  two  practices,  in  the  way  of  working  steam,  but  by  this  time  the 
reader  should  be  quite  able  to  read  the  lines.  In  Fig.  9  we  have  a  diagram  of 
rather  peculiar  appearance,  and  yet  it  is  not  many  years  ago  that  a  great 
many  engines  were  working  under  circumstances  no  more  favorable  than  is 
shown  by  this  card.  It  is  a  low  pressure  condensing  engine.  The  steam  is 
carried  half  the  stroke,  the  pressure  being  regulated  by  the  throttle  valve  in 


TWENTY  YEARS    WITH  THE  INDICATOR.  31 

the  pipe,  but  the  admission  line  is  a  little  late.  The  steam  line  is  very  well 
maintained,  but  at  what  an  expense !  While  the  expansion  line  is  somewhat 
irregular,  and  is  much  higher  at  the  termination  than  it  should  be,  from  the 
fact  that  the  valve  which  is  used  in  this  case  did  not  close  promptly  enough. 
The  condensing  is  almost  a  farce.  It  will  be  seen  that  the  valve  opened  very 
slowly,  or  that  the  condenser  took  hold  very  imperfectly ;  and  the  piston  had 
returned  nearly  half  its  stroke  before  the  condenser  had  attained  the  maximum 
vacuum,  while  the  distance  between  the  return  line  of  the  steam  and  the  line 
of  absolute  vacuum  is  about  equally  divided.  In  other  words,  the  vacuum  is 
just  about  half  what  it  should  be ;  the  atmospheric  line  of  the  instrument 
running  through  the  Indicator  lines,  and  the  absolute  vacuum  below, — without 
measurement  we  should  say  it  was  about  one-half,— and  yet  there  are  engines 
running  today  in  just  this  kind  of  practice.  This  engine  uses  double  the 


FIG.  9. 

steam  in  amount,  at  half  the  pressure,  and  the  engine  only  affords  about  half 
the  vacuum.  It  is  therefore  utilizing  something  less  than  one-third  of  the  fuel 
that  is  burned  in  the  furnace. 

Fig.  10  we  have  chosen  for  an  especial  purpose.  It  is  a  fine  outline;  the 
compression  is  an  elegant  line ;  the  steam  valve  opens  at  just  about  the  right 
point,  and  the  admission  line  is  correct.  The  expansion  line  looks  well  to  the 
eye,  but  the  style  of  engine  is  one  that  makes  a  fine  diagram,  and  most 
essentially  misleads  the  unpracticed  eye  in  its  reading.  The  diagram  in  ques- 
tion is  made  from  a  non-condensing  engine,  at  a  slow  rate  of  speed,  from  what 
is  known  as  the  Sickels  valve-gear,  using  single  or  double  poppet  valves. 

The  clearance  of  this  engine,  by  reason  of  the  valves  used,  is  enormous, 
but  they  have  a  chronic  way  of  leaking,  so  that  the  expansion  line  in  this 
engine,  except  the  whole  clearance  be  known,  is  of  no  use  whatever  in  erecting 
upon  it  a  theoretical  curve  in  order  to  measure  its  efficiency.  And  while  the 
outline  is  agreeable,  with  the  exception  of  the  undulations  in  the  expansion 
curve,  it  bounds  a  waste  of  fuel  that  would  not  be  tolerated  today  by  any  sane 
man  who  had  to  pay  for  fuel  himself,  and  could  not  be  used  by  any  concern 
who  paid  for  their  fuel  or  meant  to  pay  their  bills.  When  the  valves  and  seats 


32  TWENTY  YEARS    WITH  THE  INDICATOR. 

are  new  and  tight,  it  works  with  much  more  economy  than  when  any  little 
trouble  has  arisen  from  the  wear  of  the  valve.  But  the  clearance  is  so  very 
large  that  economy  is  absolutely  out  of  the  question.  The  question  has  several 
times  been  asked  us:  Is  it  possible  for  an  engine  that  is  not  economical  to 
make  a  handsome  Indicator  card  ?  This  is  an  example  and  an  answer  to  that 
question. 

The  Indicator  card,  in  itself,  is  of  very  little  value,  except  all  the  circum- 
stances that  surround  it  are  made  known  from  the  positive  standpoint  of 
absolute  measurement.  In  this  case,  if  the  actual  clearance  was  known,  the 
termination  of  the  line  of  expansion  would,  without  doubt,  be  above  the 
proper  termination  of  the  theoretical  curve ;  for  the  clearance  is  very  large, 
and  whatever  amount  of  clearance  is  found  in  an  engine  is  a  constant  quantity 
that  must  measure  out  an  amount  of  steam,  which  does  no  good  beyond  rilling 
a  certain  amount  of  dead  room  at  every  revolution  of  the  engine. 


FIG.  10. 

•••      t  "-' -  -•-"-•    -  •'• 

As  steam  is  a  fluid  which  is  capable  of  measurement  just  as  much  as 
water  or  milk,  do  not  allow  an  engine  builder  to  talk  you  into  the  use  of  a 
large  clearance,  by  any  roundabout  method  of  argument ;  for  if  you  are  using  a 
cut-off  engine,  the  amount  of  steam  wasted  in  the  clearance  must  be  filled  with 
live  steam,  while  the  valve  is  open,  and  the  ratio  of  expansion  has  nothing  to 
do  with  it.  The  amount  of  steam  which  you  measure  out  in  this  way  is  for 
each  end  of  each  revolution,  and  the  waste  is  therefore  as  many  times  the 
excess  of  clearance  as  your  engine  makes  strokes  per  day,  month,  or  year. 

In  Fig.  10  there  is  positively  no  back  pressure,  and  back  pressure  is  no 
more  necessary  in  a  well  constructed  engine  than  a  leaky  piston  head ;  and 
except  some  obstacle  is  offered  to  the  exhaust,  an  engine  should  exhaust  at  no 
back  pressure,  without  some  visible,  sensible  reason,  as  in  the  case  of  very 
extended  exhaust  pipes,  exhausting  through  small  pipes  to  heat  rooms,  or 
some  such  reason  as  that.  An  engine  making  the  card,  Fig.  10,  although  high 


TWENTY  YEARS    WITH  THE  INDJCATO& 


33 


pressure,  will  do  nearly,  if  not  quite,  double  the  work  with  the  same  coal  as 
the  engine  which  makes  the  card,  Fig.  9;  while  if  Fig.  10  should  be  set, to 
work  with  a  proper  condensing  apparatus,  it  would  do  a  very  large  percentage 
more  than  the  engine  upon  which  Fig.  9  was  made,  with  the  same  amount  of 
coal.  '.'  >-*i  ovtnv 


LESSON  IV. 


IN  this  lesson  we  shall  come  at  once  to  the  practical.     Both  diagrams 
shown  are  from  the  same  engine,  and  taken  upon  the  same  day. 


FIG.  ii. 

Fig.  ii  is  not  an  uncommon  diagram,  although  this  was  from  a  modern 
built  cut-off  engine,  by  Wheelock.  The  engineer  in  this  case  had  beconie 
dissatisfied  with  himself  and  everybody  else,  and  he  was  one  of  those  men  who 
do  not  consider  an  Indicator  of  any  practical  value ;  consequently  he  had 
placed  the  valves  in  such  a  position  as  he  knew  was  correct.  The  result 
proves  that  he  was  not  correct.  The  line  at  A  represents  the  steam  pressure 
in  the  boiler,  and  is  the  same  in  both  figures,  and  it  is  erected  at  right  angles 
to  the  atmospheric  line  of  the  instrument.  Mr.  Engineer,  in  making  his 
changes,  made  the  motion  of  the  valves  very  late,  as  will  be  seen  at  B.  The 


$4  TWENTY  YEARS    WITH  THE  INDICATOR. 

valve  did  not  commence  to  open  till  after  the  piston  had  started  on  its  stroke, 
and  the  old  saying,  "  a  stern  chase  is  a  long  one,"  was  never  better  exemplified 
than  in  this  case.  The  valve  being  late  in  its  opening,  is  late  at  every  portion 
of  the  stroke.  The  steam  line  in  this  case  rises  after  the  piston  starts,  for 
when  the  valve  gets  wide  open  it  admits  more  steam  than  it  did  at  first.  The 
expansion  line  is  a  rather  awkward  affair,  while  the  exhaust  resembles  an  old- 
fashioned  shoe  toe,  and  it  is  evident  the  engine  has  too  much  back  pressure. 
At  C  there  is  a  peculiar  little  point,  caused  by  the  late  closing  of  the  exhaust 
valve;  and  after  the  piston  stops,  the  Indicator  seems  to  drop  a  couple  of 
pounds.  From  C  to  B  the  admission  line  is  very  poor. 


FIG.  12. 

Fig.  12  shows  the  diagram  a  couple  of  hours  afterward,  and  which  pre- 
sents a  very  different  appearance  indeed.  In  this  case,  the  admission  line  does 
not  come  fully  up  to  the  boiler  pressure.  The  steam  line  is  hardly  maintained 
as  it  should  be,  —  it  is  a  very  great  improvement  over  Fig.  u,  —  but  the  im- 
provement is  not  entirely  in  the  outline. 

On  these  diagrams  there  is  another  very  serious  question.  Fig.  1 1  was 
not  doing  any  more  work  than  Fig.  12, —  in  fact,  it  was  running  the  very  same 
machinery,  and  did  not  run  it  at  quite  full  speed,  —  while  the  amount  oi  coal 
used  to  produce  Fig.  1 1  was  sixteen  tons,  and  that  used  to  produce  Fig.  12  was 
twelve  tons  in  the  same  time.  Now,  this  evident  discrepancy  was  not  from 
any  particular  fault  in  the  engine  builder,  but  all  lay  in  the  fact  that  the  engi- 
neer knew  very  much  better,  in  his  own  estimation,  than  he  did  as  a  matter  of 
fact,  what  should  be  going  on  inside  the  engine  cylinder,  —  and  this  is  a  very 
common  mistake. 

Fig.  12  shows  very  much  less  back  pressure  and  earlier  exhaust,  and  a 
slight  amount  of  compression,  but  sufficient  to  arrest  the  motion  of  the  piston. 


TWENTY   YEARS    WITH  THE  INDICATOR.  35 

The  steam  valve  commences  to  open  just  about  early  enough,  and  the  steam 
is  carried  a  little  less  than  one-half  as  far  on  the  steam  line  in  Fig.  12  as  it  is  in 
Fig.  1 1 .  The  consequence  is,  less  steam  is  admitted  to  the  cylinder  to  do  the 
same  work,  less  steam  is  exhausted,  and  very  much  less  is  wasted,  and  only  by 
the  simple  and  proper  placing  of  the  valves. 

Sometimes  men  reason,  although  very  falsely,  that  they  can  tell  by  the 
motion  of  the  valve,  or  the  exhaust,  or  something  else,  how  the  engine  takes 
steam ;  but,  as  a  matter  of  fact,  no  person  can  tell  anything  about  it  till  after 
the  Indicator  is  applied,  —  and  not  then  except  the  application  be  strictly  cor- 
rect, —  and  whoever  reads  it  must  have  had  some  practice  in  reading  the  lines 
of  a  diagram.  The  two  figures  are  as  unlike  as  it  is  possible  to  make  them, 
while  the  serious  question  is :  Why  should  not  any  engine  make  Fig.  1 2  as 
well  as  Fig.  1 1 ,  while  it  costs  less  to  make  it  ?  And  the  only  answer  is  that 
the  engine  will  make  it  if  you  have  an  engineer  who  is  willing  to  steer  by  the 
Indicator.  There  is  no  trouble  whatever  in  doing  this ;  but  the  fact  is,  engi- 
neers do  not  always  like  to  learn,  and  in  many  cases  parties  in  charge  of 
manufacturing  establishments  do  not  furnish  their  engineers  with  the  materials 
with  which  to  work. 

This  is  only  a  single  lesson,  but  what  is  very  frequently  done,  and  as  a 
rule  the  men  who  do  it  are  not  the  engineers.  If  the  reader  will  figure  both 
these  diagrams  from  the  same  data,  they  will  find  a  very  serious  difference, 
and  this  difference  is  WASTE  to  the  owner,  and  is  precisely  the  measure  of 
difference  between  a  good  and  a  poor  engineer.  There  is  no  material  differ- 
ence in  the  amount  of  work  done,  although,  as  a  matter  of  fact,  the  same 
machinery  was  run  at  the  same  speed,  in  each  case,  by  the  very  same  engine; 
and  it  will  be  good  practice  to  figure  the  difference  in  an  engine  of  18  X  42, 
running  65  revolutions,  and  see  how  much  was  wasted. 


LESSON  V, 

-     '  '    -vV 

IN  this  lesson  we  have  two  interesting  subjects.  One,  a  high  speed 
engine,  12^2  by  16  inch  cylinder,  running  160  revolutions,  diagram  with  a  50 
spring.  This  diagram  (Fig.  13),  as  a  general  outline,  approximates  very 
closely  to  locomotive  practice.  The  engine  takes  steam  at  A,  and  the  steam 
is  shot  into  the  cylinder,  and  immediately  decreases  in  pressure  to  a  very  great 
extent,  from  A  to  B,  —  perhaps  we  have  made  the  line  a  trifle  too  long, — 
about  one-third  of  the  stroke.  This  is  very  nearly  the  steam  line.  The 
pressure  at  A  is  75  pounds.  At  B  it  is  50  pounds.  We  have  no  data  upon 


TWENTY  YEARS    WfTH  THE  INDICATOR. 


which  we  can  figure  or  lay  out  the  curves.  Hence,  we  cannot  say  whether  the 
expansion  line  of  the  diagram  is  correct  or  not.  The  exhaust  valve  opens  at 
A  B,  nearly  one-sixth  of  the  stroke.  The  exhaust  line  is  very  good.  There 
is  no  back  pressure,  but  the  exhaust  valve  closes  again  very  nearly  at  C,  which 
is  one-half  of  the  stroke.  The  compression  line  in  this  case  is  well  formed, 
but  whether  it  is  an  economical  one  or  not  can  only  be  judged  by  data  which 
we  are  not  possessed  of.  The  outline  of  this  diagram  is  peculiar,  to  say  the 
least,  and  we  have  no  doubt  it  is  interesting,  if  we  had  the  whole  facts,  from 


FIG.  13. 

which  we  could  make  deductions  as  to  its  economy,  or  otherwise.  The  steam, 
in  this  case  does  not  obtain  access  to  the  piston  as  readily  as  it  should.  The 
line,  A  to  B,  indicates  what  the  steam  line  at  induction  pressure  would  be,  for 
whatever  length  of  stroke  it  is  carried;  and  the  line  from  the  horizontal  to  B 
shows  the  pressure  line  from  the  opening  of  the  valve  to  the  cutting  off.  The 
clearance  of  this  engine,  although  very  small,  shows  a  very  good  expansion 
curve,  Bu-t  if  the  clearance  exceeds  4  or  5  per  cent.,  the  curve  would  not 
rank  well.  We  do  not  rriean^  well  as  to  the  ideas  of  some  engineer  or  builder 
—  we  mean  well  as  to  the  coal  pile. 


FIG.  14. 


Figs.  14  and  15  are  from  a  Corliss  engine,  and  in  both  these  cases  the 
steam  valve  opens  late.  The  admission  line  is  therefore  tardy.  The  steam 
line  m  Fig.  15  is  somewhat  peculiar,  as  it  carries  the  induction  pressure  very 


TWENTY  YEARS    WITH  THE  INDICATOR.  37 

squarely  for  a  short  distance,  when  it  drops  off;  and,  'from  the  formation  of  the 
line,  we  should  infer  more  steam  entered  the  cylinder.  We  have  not,  in  this 
case,  the  clearance  upon  which  to  erect  a  theoretical  expansion  curve.  Our 
purpose  is  not  to  treat  this  diagram  from  a  theoretical  stand-point,  but  to  draw 
from  it  a  practical  lesson  for  those  who  are  not  too  hard-headed  to  learn. 
This  is  another  expensive  practical  lesson,  where  men  overreach  themselves 
in  their  attempt  to  do  their  own  engineering.  The  cylinder  of  this  engine  is 
23  inches  in  diameter,  60  inch  stroke,  75  revolutions.  The  diagrams  are  taken 
with  a  40  spring. 

Fig.  14  shows  more  back  pressure  than  Fig.  15.  In  either  case  the 
amount  is  very,  large.  From  the  time  the  engine  takes  steam  until  the  valve 
closes,  and  the  admission  of  steam  to  the  cylinder  is  stopped,  a  considerable 
decrease  of  pressure  upon  the  piston  is  shown.  The  shape  of  this  line  tells 
the  practiced  eye  plainly  that  there  is  some  reason  for  it.  The  line,  for  a 
portion  of  its  distance,  is  almost  a  right  angled  triangle,  or  two  sides  of  it, 
when  compared  with  the  upright  line,  A.  The  formation  of  the  line,  therefore, 
shows  that  the  cylinder  is  calling  for  more  steam  than  the  port  is  able  to 
supply.  In  this  case,  the  reason  is  a  very  simple  one.  The  parties  who  are 


FIG.  15. 

running  this  engine  bought  a  200  horse-power  machine ;  it  is  indicating  350  to 
380  horse-power,  or  nearly  double  what  it  was  ever  intended  to  do  economi- 
cally. Investigation  into  this  question,  of  a  very  recent  date,  by  a  competent 
engineer,  develops  the  fact  that  the  engine  is  working  at  double  the  load  it  was 
ever  intended  for,  and,  with  all  its  disadvantages,  upon  29  pounds  *of  steam  per 
indicated  horse-power,  upon  a  test;  These  diagrams  do  not  show  an  econom- 
ical use  of  steam,  from  the  fact  that  the  load  upon  the  engine  is  so  large  that 
the  ratio  of  expansion  is  entirely  too  small.  More  steam  is  required  to  drive 
the  load  than  the  steam -ports  will  properly  handle,  so  far  as  economy  goes. 
That  is  to  say,  the  amount  of  steam  required  at  each  end  of  each  stroke,  is  so 
much,  that  the  capacity  of  the  ports  will  not  admit  it  all,  at  the  pressure 
required,  or  furnished  by  the  boiler;  that  the  amount  of  steam  admitted  is 


38  TWENTY   YEARS    WITH  THE  INDICATOR. 

more  than  will  be  admitted  at  boiler  pressure ;  and  upon  the  other  end  of  the 
stroke,  the  volume  of  steam,  after  expansion,  ;s  more  than  the  exHaust  ports 
will  readily  relieve  the  engine  of;  so  that  a  loss  is  made  at  both  ends,  —  a 
radical  loss  of  initial  pressure,  and  a  loss  of  resistance  by  back  pressure  after 
the  steam  has  expanded,  or  done  all  its  work.  For  all  this  fault  there  is  only 
one  remedy:  less  load,  or  a  larger  engine.  In  this  case,  we  presume  the 
engine  will  be  charged  with  what  is  really  the  fault  of  the  owners  or  managers, 
and,  without  much  doubt,  they  will  be  entirely  blind  to  the  fact  that  they  are 
themselves  the  cause  of  a  costly  steam  power.  Our  next  lesson  will  show  a 
modern  built  engine,  which  the  reader  will  do  well  to  contrast  with  this  over- 
loaded Corliss.  It  is  no  use  to  expect  to  load  a  300  horse-power  engine  to 
560  horse-power,  and  get  an  economical  result  in  the  use  of  steam.  But  there 
are  people  in  the  world  who  are  just  complacent  enough  to  suppose  that  one 
pound  of  coal  will  do  an  immense  amount  of  work  —  if  they  only  direct  the 
way  in  which  it  shall  be  used. 

In  these  lessons  we  have  nothing  to  do  with  the  theoretical,  beyond  the 
simple  comparison,  believing  that,  as  facts  are  facts,  and  these  examples  are 
all  from  actual  use,  our  readers,  who  are  honest  with  themselves  and  can 
learn  from  example,  cannot  fail  to  profit  by  them.  In  too  many  cases  the 
use  of  steam  is  an  expensive  luxury,  and  the  overloading  of  an  engine  is  not 
the  least  expensive.  And  aside  from  the  danger  incurred,  the  liability  of  a 
complete  smash-up  or  stoppage,  it  must  also  be  borne  in  mind  that  all  of  these 
circumstances  tend  to  involve  danger  to  the  lives  of  all  those  immediately  in 
reach,  —  and  this  is  a  factor  which  is  not  always  taken  into  account  or 
consideration. 


LESSON   VI. 


IN  this  lesson  we  have  a  rather  interesting  and  instructive  subject.  The 
diagrams  furnished  are  both  from  the  same  engine,  are  from  actual  practice, 
and  were  taken  for  the  purpose  of  ascertaining  what  economy  the  engines  are 
working  with.  The  size  of  the  engine  is  6  X  14  inches,  running  220  strokes, 
or  a  trifle  more,  giving  an  indication  of -f-  17  horse-power,  with  an  assumed 
clearance  in  the  construction  of  the  theoretical  curve  of  three  per  cent,  of  the 
volume  of  the  cylinder  capacity.  Subsequently  to  the  trial  the  piston  was 
found  to  be  leaking  badly.  The  compression  on  this,  as  most  other  high-speed 


TWENTY   YEARS    WITH  THE  INDICATOR.  39 

engines,  is  a  considerable  factor,  much  more  than  we  should  like  to  see.  But 
it  is  a  part  of  the  motion  of  the  valve.  If  it  opens  early  for  the  exhaust,  it 
must  necessarily  close  very  early,  and  as  there  is  no  limit  of  changing  the 
throw  of  the  one  witnout  the  other,  then  the  whole  matter  has  to  be  averaged. 
The  peculiar  kink  at  the  upper  right-hand  corner  of  each  card  shows  the 
action  of  this  compression,  and  the  opening  of  the  valve.  In  one  case  the 
steam  line,  properly  speaking,  is  theoretically  correct,  with  the  exception  that 
it  does  not  rise  nearly  as  high  as  the  steam  pressure ;  while,  in  the  other  case, 
the  valve  does  not  open  as  it  should,  and  the  steam  line  falls  away  rapidly, 
until  the  real  point  of  cut-off  is  lost,  and  the  line  becomes  very  irregular  on 
the  expansion  curve.  The  back  pressure  amounts  to  but  very  little,  indeed, 


FIG.  16. 

while  the  compression  line,  theoretically  or  mechanically,  is  quite  too  much, 
and  approximates  to  locomotive  practice,  where  it  is  very  necessary  to  bring 
the  reciprocating  parts  of  the  engine  to  perfect  rest  by  a  free  use  of  steam. 
The  compression  occurs  here  at  about  one-sixth  of  the  stroke,  or  rather  more 
than  that.  The  curve  in  this  case  includes  the  clearance,  and  is  seen  to  be 
materially  above  what  was  expected  of  it,  approaching  nearer  the  expansion 
line  at  the  point  where  expansion  ceases.  Taking  the  cut-off  at  the  apparent 
point,  including  clearance,  it  is  .295  of  the  stroke.  The  feed- water  consumed 
during  the  trial  was  40.78  pounds  per  hour.  The  power  of  this  engine  is 
small.  We  have  not  all  the  facts  in  connection  with  it  as  to  the  effectiveness 
of  the  boiler.  It  is  only  one  instance  of  a  pretty  card  in  its  general  outline, 
which,  when  it  comes  to  be  surrounded  by  the  facts,  makes  a  very  expensive 


40  TWENTY   YEARS    WITH  THE  INDICATOR. 

power.  The  action  of  the  valve  is  such  that  it  requires  a  large  amount  of 
steam,  and  whatever  the  amount  of  leakage  may  have  been,  it  was  probably 
not  enough  to  radically  increase  the  amount  of  steam  used  per  hour.  ;  i  ...- 


FIG.  17. 


LESSON  VII. 


THE  originals  from  which  the  engravings  were  made  for  this  lesson,, 
sent  us  by  a  man,  with  the  statement  that  he  is  a  practical  engineer,  —  but/! not 
an  expert,  —  and  that  he  \g  trying  to  learn  something-  by  the  practical  applica- 
tion of  the  Indicator  to  different  Steam  engines.  He  asked  several  questions, 
and  sent  three  sets  of  cards  from  two  different  engines.  The  cards  contained 
in  themselves  a  whole  lesson,  and  we  propose  to  answer  his  questions  from  a 
practical  point  of*  view. 

The  diagrams  (18  and  19)  are  taken  from  a  Harris -Corliss  engine,  36  X 
14  inches,  speed  65  revolutions,  55  pounds  boiler  pressure,  30  scale.  Our 
correspondent  asks :  "  What  are  the  reasons  for  the  fluctuations  shown  by 
the  governor?  I  suppose,  in  figuring  these,  it  would  be  proper  to  take ; the 
mean.  When  the  engine  is  loaded,  the  trips  of  the  cut-off  seem  to  act  all 


TWENTY   YEARS    WITH  THE  INDICATOR.  41 

right,  but  When  she  is  not  loaded,  the  fluctuations  are  very  wide.     What  is  the 
reason  ? 

In  the  first  place,  these  diagrams,  for  practical  purposes,  such  as  adjusting 
the  valves  of  an  engine,  or  ascertaining  the  actual  pressure  of  each  end  of  the 
cylinder,  are  absolutely  worthless.  They  have  no  value  whatever,  and  for  this 
reason :  The  diagrams,  as  shown  here,  are  taken  by  a  connection  leading  from 
either  end  of  the  cylinder  to  the  center  of  the  cylinder,  at  which  place  a  three- 
way  cock  is  probably  used,  and  in  the  time  required  to  change  the  three-way 
cock  from  one  side  to  the  other,  the  load  of 
this  engine  may  vary  from  20  to  30  horse- 
power. If  the  diagrams  were  taken  as 
quickly  as  possible,  they  cannot  both  be 
taken  upon  the  same  stroke;  consequently 
the  value  of  the  comparison  between  the 
different  ends  is  lost.  In  the  loaded  engine 
and  the  unloaded,  the  same  readings  are 
apparent.  We  have  drawn  the  atmospheric 
lines ;  and  the  lines,  A  B,  upon  each  side  of 
the  diagrams,  are  at  exactly  right  angles  to 
the  atmospheric  line  of  the  instrument.  The 
admission  line  upon  one  of  these  cards  falls 
away  from  the  upright ;  consequently  the 
induction  valves,  or  steam  valves,  are  too 
late  in  their  movements  in  opening.  This 
is  applicable  to  each  one  of  the  four  dia- 
grams. It  will  be  noticed  that  the  crank 
end,  upon  each  set  of  cards,  does  not  give 
the  same  initial  pressure  as  the  head  end, 
and  if  Indicators  were  used  upon  each  end  of 
the  cylinder;  —  this  would  undoubtedly  be 
found  to  be  the  fact  in  all  the  cards.  The 
reason  for  this  is  very  apparent.  The  crank 
end  is  much  later  in  taking  steam  than  the 
head  end.  As  the  piston  commences  to 
move  away  from  the  head  of  the  cylinder 
before  the  steam  valve  opens  at  all,  and  the 
crank  valve  is  much  later  in  opening,  with 
reference  to  the  motion  of  the  piston,  than 
the  head  end,  it  never  gets  open  wide 
enough  to  admit  the  full  pressure,  from 

FIG.  18. 

the  fact  that  the  volume  of  the  cylinder  is 

increased  so  much  faster  by  the  movement  of  the  piston  than  the  capacity  of 

the  steam-port  will  supply.     The  head  end,  upon  both  diagrams,  has  several 


42  TWENTY  YEARS    WITH  THE  INDICATOR. 

pounds  more  initial  pressure  than  the  crank  end ;  and  although  the  head  end 
is  late  in  the  motions  of  the  valve,  the  valve  opens  relatively  sooner  than  in 
the  crank  end. 

The  way  of  connecting  the   Indicator   to    the    middle    of  the   cylinder, 
although  altogether  wrong,  is  the  favorite  method  adopted  by  almost  all  the 

high-speed  engine  builders,  for  it  shows  their  line 
of  admission  nearer  to  a  right  angle  to  the  atmos- 
pheric line  of  the  instrument,  and  it  is,  therefore,  a 
point  of  advantage  with  them.  They  are  obliged 
to  open  their  valves  very  quickly,  or  to  use  an  enor- 
mous amount  of  compression.  The  little  amount 
of  time  lost  by  the  steam  running  the  whole  length 
of  this  pipe,  if  only  12  inches,  makes  a  certain  cor- 
rection, which  is  in  their  favor.  On  the  Corliss 
engine,  as  in  this  case,  the  admission  of  steam  is 
shown  late  upon  the  diagram,  and,  no  doubt,  if  the 
Indicator  was  connected  by  the  shortest  possible 
connection  to  either  end  of  the  cylinder,  this  motion 
would  be  somewhat  diminished,  but  the  essential 
feature  of  the  valves  opening  late  would  be  found  to 
be  a  fact. 

Our  correspondent  asks  why  the  regulator  fluc- 
tuated more  upon  the  crank  end  than  upon  the  head 
end.  The  reason  is  perfectly  plain.  When  the 
engine  takes  steam  upon  the  head  end  of  the  piston, 
it  takes  a  larger  amount  than  it  can  take  upon  the 
crank.  The  tendency  of  this  is  to  increase  the 
speed  of  the  engine.  While  the  piston  is  making 
the  stroke  toward  the  crank  end,  the  speed  is  some- 
what accelerated,  the  regulator  ball  slightly  raised, 
and  the  crank  end  of  the  engine,  when  it  takes 
steam,  is  tripped  just  that  amount  shorter  in  order 
to  maintain  the  proper  speed  which  the  engine  is 
set  to  run  at.  Having  taken  this  amount  of  steam, 
the  balls  drop,  and  the  head  end  trips  longer.  In 
other  words,  the  head  end  is  doing  considerable 
more  work  than  the  crank  end,  and  the  crank  end 
is  endeavoring  to  adjust  all  the  time ;  and  if  the 

Indicators  could  be  applied  to  both  ends  of  the  engine,  and  simultaneous 
diagrams  taken,  there  is  hardly  any  doubt,  in  our  mind,  that  the  fluctua- 
tion would  be  found  as  wide  upon  the  head  as  they  are  shown  upon  the 
crank  end.  This  we  have  proven,  over  and  over  again  in  practice.  One  end 
of  the  engine  is  doing  more  than  the  other,  and  the  other  end  is  trying  all  the 


TWENTY  YEARS   WITH  THE  INDICATOR.  43 

time  to  strike  an  average  and  keep  its  speed;  consequently  the  regulator 
changes  the  point  of  cut-off  at  every  single  stroke  of  the  engine.  This  is  not 
so  apparent  in  the  diagram  taken  with  the  whole  load  on,  because  the 
percentage  of  variation  is  so  very  much  less  in  proportion  that  it  does  not 
show  in  the  lines. 

It  would  not  be  proper  to  take  the  mean  of  either  one  of  these  two 
diagrams  as  the  actual  amount  of  work  done.  It  would  show,  to  be  sure, 
what  was  being  done  at  the  instant  the  diagrams  were  taken,  but  an  average 
of  36  upon  one  end  and  16  upon  the  other,  does  not,  by  any  means,  give  the 
actual  average  of  26  horse-power  as  the  work  required  to  overcome  the 
resistance.  If  our  engineer  friend  will  throw  away  his  three-way  connection, 
put  it  in  the  scrap -pile,  and  leave  it  there  forever,  make  the  shortest  connec- 
tion possible  with  each  end  of  the  cylinder,  borrow  an  Indicator,  —  if  he  does 
not  own  two,  —  and  apply  these  Indicators  to  both  ends  of  the  engine,  he  will 
find,  we  think,  just  what  we  have  laid  out  for  him.  Then,  if  he  finds  the 
admission  line  a  little  late,  let  him  shorten  up  his  connection  until  the  angle  of 
the  lines,  A,  B,  and  the  admission  line  from  the  point  of  compression  shall  be 
one  line  instead  of  two,  get  his  engine  so  that  it  takes  steam  sharp  upon  the 
center,  —  not  a  particle  before,  —  then  watch  his  engine  for  an  hour,  and  when- 
ever he  changes  the  trip -dogs,  changing  both  whenever  he  changes  one, 
putting  one  back  and  the  other  forward,  figure  his  diagrams,  —  and  upon  an 
engine  of  this  size  he  should  not  allow  a  variation  of  more  than  two  or  three 
horse-power,  —  taking  care  to  adjust  the  engine  as  nearly  as  possible  from  the 
full  load ;  he  will  then  find,  if  he  cuts  the  belt  off  his  fly-wheel,  that  the  engine 
will  cut  off  with  the  lightest  load,  both  ends  at  the  same  stroke,  and  the  variation 
in  the  amount  of  work  done  should  be,  and  will  be,  with  proper  adjustment, 
very  small  indeed.  He  will  find  that  his  regulator  will  assume  a  very  much 
more  settled  condition  —  it  will  not  be  reaching  with  every  strrke.  He  will 
find  that  the  confusion  of  lines  will  disappear,  and  that  this  will  not  be  all. 

An  engine  of  150  horse-power  was  recently  indicated  by  us  at  the  request 
of  a  party  who  was  anxious  to  ascertain  if  the  Indicator  had  any  value.  The 
mean  of  the  first  diagrams,  taken  from  simultaneous  cards,  showed  168  horse- 
power. The  head  end  was  doing  fully  15  per  cent,  more  than  the  crank  end. 
After  the  engine  had  been  adjusted,  the  mean  of  two  cards  was  154  horse- 
power, with  a  variation  of  less  than  4  horse-power  as  the  mean  of  1 2  sets  of 
simultaneous  cards.  The  difference  between  154  and  168  was  being  thrown 
away ;  in  other  words,  the  engine  was  requiring  steam  capable  of  maintaining 
1 68  horse-power,  when,  as  a  matter  of  fact,  the  load  only  required  154  horse- 
power. The  speed  of  the  readjusted  engine  was  much  nearer  correct  than 
that  of  the  engine,  when  one  end  was  reaching  after  the  other  alternately. 

There  is  a  point  here  that  engineers  should  understand,  and  that  is,  that 
the  variations  of  one  end  of  the  cylinder  reaching  after  the  other,  when  it  is 
not  properly  adjusted,  calls  for  the  use  of  more  steam  to  do  the  same  work. 


on 


44  TWENTY   YEARS    WITH  THE  INDICATOR. 

because  it  does  not  do  its  .work  properly.     The  amount  of  coal  require*    , 
this  engine  was  26  tons,  before  adjustment;  after  the  adjustment,  the  patdes 
reported  that  in  the  same  length  of  time  20^  tons  did  all  the  work  for  three 

successive  weeks.  The  result  of  the  mat- 
ter has  been,  the  party  has  ordered  a  pair 
of  Indicators,  and  his  engineer  is  to  make 
himself  familiar  with  them,  and  take  dia- 
grams every  day.  This  is  entirely  a  prac- 
tical lesson,  and  there  are  hundreds  of 
engines  running  worse  than  this,  which 
are  considered  to  be  doing  very  well. 

The  diagrams  20  and  21  are  from  an 
1 8  X  42  inch  automatic  cut-off  engine,  built 
by  Geo.  A.  Rollins  &  Co.,  Nashua,  N.  H., 
with  valves  of  the  Corliss  style,  running- 
72  revolutions  per  minute.     The  scale  is 
30,  high  pressure,  the  clearance  being  2^ 
per  cent.     The  smaller  diagrams,  or  the 
lightest  load,  show  that  the  head  end  is 
doing  the  most  work.     The  motion  of  the 
valves  is  a  little  late  upon  each  end,  as 
will  be  seen  by  reference  to  the   upright 
line.     The  crank  end  cuts  off  very  sharp, 
while  the  head  end  does  more  work  than 
the  crank  end.     This  is  purely  a  question 
of  the  adjustment  of  the  valves.      These 
cards  are  very  clean  in  the  track  of  the 
Indicator  pencil.     The  card,  with  several 
lines   upon    it,  is   from  the  same  engine 
under  varying  loads,  and  the  lines  of  the 
instrument  have  been  traced  as  nearly  as 
possible. 

In  Fig.  21,  A  is  the  atmospheric  line 
of  the  instrument,  the  back  pressure  valve 
being  closed.  This  engine  is  in  the  Bay 
State  Sugar  Refinery,  Boston,  and  the  vari- 
ation in  the  lines  is  caused  by  the  throwing  off  or  on,  two  or  three  at  a  time,  of  the 
centrifugal  machines  used  in  the  works,  which  take  from  25  to  50  horse-power 
each  to  start.  The  engine  carries  steam  the  full  length  of  the  stroke,  in  an 
almost  absolutely  straight  line.  This  could  not  be  done  unless  it  had  sufficient 
valve-port  room,  while,  in  cutting  off  at  nearly  three-fourths  of  the  stroke,  or 
at  about  one-half  of  the  stroke,  the  lines  are  very  good.  The  exhaust,  in  this 
case,  we  cannot  tell  exactly  about,  as  the  back -pressure  valve  is  closed.  But 


TWENTY  YEARS    WITH  THE  INDICATOR.  45 

it.  is  evident,  from  the  general  conformation  of  the  three  lines,  that  the  exhaust 
valve  has  a  capacity  nearly  equal  in  exhausting  to  carrying  steam  almost  the 
full  length  of  the  stroke.  When  the  centrifugal  machines  are  thrown  on,  they 
are  required  to  be  brought  to  speed  as  soon  as  a  half  minute,  which  makes  a 
very  large  change  in  the  load  of  the  engine,  or  the  requirements.  In  this 

case,  however,  the  engine  seems  to  be  fully  able 
to  answer  these  requirements,  and  the  variation  in 
speed  was  very  slight.  But  with  carrying  the 
steam  the  whole  length,  it  necessarily  reduced  the 
speed  of  the  engine  somewhat,  • —  else  the  cut-off 
would  have  acted.  If  anything,  the  exhaust 
valves  of  this  engine  should  open  a  little  earlier 
than  they  do.  There  is  hardly  compression 
enough  in  it,  and  the  lines  of  all  three  diagrams 
which  are  traced,  show  that  the  exhaust  is  some- 
what retarded  at  the  commencement  of  the  return 
of  the  stroke  of  the  piston.  The  opening  of  the 
valves  to  admit  steam  is  slightly  late,  —  only 
slightly  so,  —  while  the  steam  lines  are  most 
excellently  well  produced.  The  outline  of  B, 
Fig.  21,  shows  that  the  exhaust  line  is  almost  as 
perfect  as  the  steam  line  of  the  largest  figure 
The  turning  of  the  instrument  shows  it  slightly 
rounded,- — in  other  words,  that  there  is  a  small 
accumulation  of  steam  in  the  way  of  retardation. 
If  the  outlines  are  correctly  traced  in  the  figure 
by  the  eye  of  the  reader,  these  will  be  found  to 
increase  as  the  load  increases,  by  the  carrying 
of  steam  further  on  the  stroke.  In  other  respects, 
the  lines  corroborate  the  outline,  making  a  work- 
ing which  should  be  very  satisfactory,  both  as 
regards  speed  and  economy.  As  a  general  rule, 
engineers  do  not  pay  attention  enough  to  what 
seems  to  them  trifling  indications  of  variation. 
Every  retardation  of  the  exhaust  upon  the  small- 
est diagram,  is  multiplied,  as  the  amount  of  steam  is  let  into  the  cylinder 
to  overcome  an  increased  resistance ;  and  the  little  points  should  be  carefully 
attended  to,  in  order  that  they  shall  not  become  serious  ones  with  the  increase 
of  the  load.  The  cushioning,  or  compression,  is  quite  too  little  upon  this 
engine,  and  if  the  amount  of  motion  at  the  commencement  of  the  exhaust  is 
put  upon  the  end  of  the  exhaust,  or,  in  other  words,  if  the  exhaust  is  opened 
earlier,  it  will  close  as  much  earlier  as  it  is  opened.  You  will  therefore  reduce 
the  back  pressure  at  the  commencement  of  the  exhaust,  and  increase  the 


46  TWENTY  YEARS    WITH  THE  INDICATOR. 

amount  of  compression  by  the  closing  of  the  exhaust,  both  of  which  are 
advantageous  in  economy,  and  are  certainly  advantageous  to  the  gooa 
working  of  the  machine.  In  the  smaller  cards,  or  those  which  indicate  the 
smallest  load,  the  amount  of  steam  used  by  the  head  end  is  more  "than  that 
used  by  the  crank  end.  If  this  were  balanced,  the  engine  would  work 
smoother,  and  there  is  no  difficulty  in  balancing  it  if  you  have  Indicators  and 
a  little  patience.  And  the  nearer  right  this  can  be  done,  the  better  production 
will  be  obtained  regularly  from  the  engine.  Little  matters  are  the  important 
ones  wherever  steam  power  is  used,  and  in  no  case  is  it  more  essentially 
important  than  in  noticing  little  variations  by  the  Indicator,  when  it  is  applied. 
The  width  of  a  pencil  line  upon  the  Indicator  diagram  does  not  appear  to  be 
much.  At  the  same  time,  it  may  be  an  important  feature  in  determining 
where  the  trouble  lies,  and  should  be  watched  very  closely,  and  no  changes 
should  be  made  without  carefully  considering  whether  everything  is  tight  and 
just  right ;  for  the  value  of  an  Indicator  diagram  increases  precisely  in  the 
ratio  that  you  give  it  care  or  attention  in  the  manipulation,  and  valuable  in 
results  only  as  you  are  accurate  and  correct  in  obtaining  them. 


LESSON  VIII. 

THE  examples  in  this  lesson  answer  an  often  repeated  question,  Are  simul- 
taneous diagrams  of  any  especial  value  over  those  which  are  not  simultaneous? 
The  diagrams  which  we  represent  are  not  simultaneous  diagrams  for  the  whole 
set.  Each  pair  of  diagrams  were  taken  at  the  same  time,  but  not  upon  each 
cylinder  of  the  engine  at  the  same  time.  There  is,  therefore,  more  variation 
than  there  would  be  if  they  were  simultaneous  diagrams.  But  these  diagrams 
represent  another  important  feature.  They  were  taken  from  a  Corliss  engine 
which  has  been  in  use  nearly  or  quite  seven  years,  the  valves  of  which  have 
never  been  bored,  turned,  or  changed.  It  is,  therefore,  a  very  fair  expression 
of  the  value  of  the  Corliss  engine,  in  reference  to  the  valves  remaining  tight 
while  doing  the  constant  regular  work. 

In  the  next  lesson  we  shall  produce  diagrams  from  high-speed  engines, 
taken  from  both  ends  of  a  pair  of  engines,  and  from  each  one  of  the  engines 


TWENTY  YEARS    WITH  THE  INDICATOR.  47 

at  the  same  instant  of  time.  A  comparison  will  aptly  illustrate  the  value  of 
simultaneous  diagrams,  which  are  very  much  underestimated  by  engineers  in 
general,  as  well  as  by  engine  builders,  and  their  men  who  set  up  and  start 
engines. 


LESSON  IX 

THE  diagrams,  Figs.  22  and  23,  are  from  the  Social  Mills,  Woonsocket, 
R.  I.  The  cylinders  are  30  X  72  inches,  48  revolutions  per  minute,  with  a  40 
spring,  working  three-quarters  condensing.  The  figures  in  each  one  of  the 
cards  represent  the  area  as  measured  by  the  planimeter.  These  figures  may, 
for  comparison,  be  called  horse-power;  for,  if  reduced  to  horse-power,  the 
amounts  would  represent  precisely  the  same  ratio  that  these  figures  do.  The 
left-hand  engine  is  doing  the  most  work,  as  the  cards  are  taken,  if  they  were 
simultaneous,  but  the  load  may  have  varied  between  them.  The  left-hand 
machine  works  all  condensing.  The  back  end  shows  490,  the  front  end,  513; 
while  the  right-hand  back  end  condensing  is  488,  the  right-hand  front  end 
high  pressure  is  376.  The  right-hand  engine  is  working  with  about  the  same 
amount  of  cut-off,  and  the  front  end,  high  pressure,  is  doing  almost  the  same 
amount  of  work  as  the  back  end  without  the  vacuum.  This  could  be  very 
easily  adjusted  by  the  use  of  the  Indicator,  if  it  was  desired  so  to  do.  Let  it 
carry  steam  a  trifle  longer  and  it  would  do  as  much  as  the  back  end ;  but  all 
these  points  are  practically  those  of  fancy,  with  the  average  engineer,  though 
not  in  a  practical  sense  fanciful  points. 

There  are  some  especial  features  about  these  cards.  The  valve  gear  upon 
this  engine  has  not,  perhaps,  the  same  delicacy  of  adjustment  as  the  motion 
Mr.  Corliss  is  now  building ;  therefore  the  toe  of  the  vacuum  is  not  so  abrupt, 
and  the  engine  is  not  working  with  as  much  perfection  as  would  be  desirable 
if  the  valve  gear  could  work  to  an  exact  adjustment.  We  say  exact  adjust- 
ment, for  if  an  engine  has  been  working  several  years,  the  valves  seat  them- 
selves ;  and  if  the  throw  or  travel  of  the  valves  should  be  changed,  the  engine 
would  be  apt  to  leak  steam  until  the  valve  seated  itself  in  its  new  position. 
For  this  reason,  the  adjustment  of  the  valves  of  an  engine  should  be  made  not 


48  TWENTY   YEARS    WITH  THE  INDICATOR. 

less  than  three  or  four  times  each  year,  as  in  that  case  the  valve  never  becomes 
seated  so  deep  but  that  it  will  readily  accommodate  itself  to  its  new  position. 

The  admission  line  in  all  these  cards  is  very  nearly  correct,  —  we  might 
say,  almost  exact.  The  steam  lines  are  a  little  broken  at  first,  —  whether  this  is 
in  the  faulty  motion  or  not,  we  have  no  means  of  telling,  —  but  the  admission 
of  steam  is  ample,  although  the  line  is  somewhat  ragged.  The  cut-off  is  well 
defined  in  all  the  cards,  although  not  as  sharp  as  it  would  be  in  an  engine  that 

had  been  recently  overhauled;  but 
when  we  come  to  consider  the  fact 
that  the  engine  has  been  working 
for  seven  years,  without  any  tink- 
ering, and  that  the  theoretical  curve 
applied  to  these  diagrams  covers 
92  per  cent.,  we  must  admit  that  the 
cards  are  very  fine.  The  amount 
of  power  involved  is  nearly  one 
thousand  horses.  This  is  one  of 
the  engines  reported  upon  at  the 
New  England  Cotton  Manufactur- 
ers' Association,  in  comparison,  in 
1880,  and  it  was  found  producing 
its  work  with  2.66  pounds  of  coal 
per  horse-power  per  hour,  and  is 
now  doing  much  better. 

The  expansion  line  of  all  these 
diagrams  is  very  good  indeed. 
The  steam  is  well  handled,  and, 
should  the  engine  be  improved  a 
little,  with  a  valve  gear  such  as  is 
now  being  put  upon  engines  of  this 
size,  there  is  no  reason  why  the 
amount  of  fuel  consumed  will  not 
be  made  smaller,  and  the  working 
of  the  engine  more  perfect.  But 
taking  an  engine,  which  has  done 
duty  so  long  and  so  regularly,  cov- 
ering 92  per  cent,  of  the  theoreti- 
cal,—  with  an  honest  showing, — 

we  must  admit,  at  once,  that  although  the  outlines  of  the  cards  are  not  perfect, 
they  are  very  much  nearer  perfection  than  in  some  newly-built  engines,  where 
not  quite  so  much  brains  have  been  mixed  in  their  care  and  management. 

It  is  noticeable  that  the  outlines  of  the  four  diagrams  are  almost  exactly 
identical;  a  slight  leak,  perhaps,  in  one,  is  almost  the  only  change.  The  steam 


TWENTY  YEARS   WITH  THE  INDICATOR.  49 

lines  are  very  nearly  the  same,  while  the  expansion  lines  vary  but  little.  The 
vacuum  is  very  even,  and  very  nearly  alike  upon  the  three-fourths  which  are 
used  condensing,  and  it  is  certainly 
a  credit  to  the  engineer  in  being 
able  to  show  such  a  result  after 
nearly  or  quite  seven  years  of  un- 
interrupted service.  This  engine 
drives  the  mill  by  a  gear  balance 
wheel.  The  boiler  pressure  is 
from  85  to  90  pounds ;  the  tem- 
perature of  the  hot  well,  as  re- 
corded, is  1 10,  attaining  nearly  28 
inches  of  vacuum,  even  in  August. 
One  of  the  most  noticeable 
features  is  that  of  88  pounds  of 
steam,  shown  by  the  gauge,  at  the 
time  the  cards  were  taken,  83  to 
85  is  shown  by  the  Indicator. 
This  point  is  often  ignored  in 
practice,  but  it  is,  nevertheless, 
one  of  the  most  important  prac- 
tical ones.  Steam  made  in  the 
boiler  is  of  no  more  use,  if  it  can- 
not be  used  at  full  pressure  in  the 
cylinder,  than  money  in  the  bank 
that  cannot  be  used  in  the  business 
man's  everyday  affairs, — with  just 
this  difference :  the  steam  costs 
money  to  generate,  —  and  there  is 
no  use  to  throttle  it  down  by  im- 
perfectly made  valves  and  ports, 
and  no  use  whatever  in  attempting  IG*  23' 

to  preach  economy  where  the  construction  of  an  engine  is  such  as  to  preclude 
the  realization  of  boiler  pressure  in  the  cylinder.  The  actual  vacuum  shown 
by  the  Indicator  is  almost  twelve  pounds,  and  varies  but  slightly  upon  the 
three  cards.  These  diagrams  will  bear  careful  inspection,  and,  although  not 
perfect,  they  are  very  much  beyond  the  average,  and  far  beyond  the  general 
practice  in  steam  engine  working.  The  engineer  of  this  concern  believes  in 
the  use  of  the  Indicator,  and  makes  a  daily  report  to  his  agent,  of  the  amount 
of  power,  where  it  is  being  done,  and  how ;  and  we  believe  he  must  make  a 
pretty  good  annual  return  to  the  concern  that  employs  him,  by  the  use  of  good 
judgment  and  skill  in  the  manipulation  of  his  Indicators,  and  engine. 


TWENTY  YEARS   WITH  THE  INDICATOR. 


LESSON  X. 


IN  this  lesson  we  have  another  type  of  engine,  and  a  different  way  of 

working  steam,  by  way  of  contrast.     In  this  case  we  have  the  diagrams  (Figs. 

24  and  25)  from  both  ends  of  each  cylinder  on  a  pair  of  horizontal  engines, 

all  taken  at  the  same  instant  of  time,  four 
instruments  being  used.  The  engine  in 
question  is  a  Buckeye  engine,  built  at  Sa- 
lem, Ohio.  It  is  22  inches  in  diameter  of 
cylinder,  44  inches  stroke,  90  revolutions 
per  minute,  boiler  pressure  85  pounds, 
throttle  valve  wide  open,  scale  of  spring 
40.  These  diagrams  were  taken  for  the 
purpose  of  ascertaining  the  condition  of 
the  engine,  and  the  amount  of  power 
transmitted.  The  figures  show  the  num- 
ber of  horse-power.  The  right-hand  en- 
gine is  doing  the  most  work.  The  outlines 
of  the  diagrams  are  peculiar  to  this  type 
of  engine.  The  left-hand  engine,  head- 
end, has  148^  horse-power;  crank-end, 
164  horse-power.  The  amount  of  steam 
pressure  shown,  when  the  valve  opens,  is 
66  pounds  carried  into  the  cylinder.  The 
dotted  lines  show  the  pressure  realized  as 
66,  while  the  fine  dotted  line  above  shows 
the  boiler  pressure.  The  mean  pressure 
upon  the  piston  in  the  diagram  doing  164 
horse-power,  is  21.92  pounds.  The  engine 
cuts  off  at  about  8.8  inches,  or,  say  one- 
fifth  of  the  stroke.  The  theoretical  mean 
pressure,  from  an  initial  pressure  of  66 
pounds,  the  ratio  of  expansion  being  five, 
would  be  22.01 ;  while,  if  this  engine  used 
the  boiler  pressure  shown  by  the  upper 
line,  only  6.3  inches  of  the  cylinder  would 

be  obliged  to  be  filled  with  steam  at  each  stroke,  instead  of  8.8  inches  at  a 

lower  pressure. 

These  diagrams  are  precisely  as  they  were  taken,  and  they  are  not  by  any 

means  the  worst  we  have  seen  where  engines  did  not  approximate  to  the 


TWENTY  YEARS   WITH  THE  INDICATOR.  51 

boiler  pressure.  It  is  a  very  general  thing,  indeed,  not  only  for  this  build  of 
engine,  but  for  many  others,  not  to  come  within  15  to  25  pounds  of  the  boiler 
pressure ;  and  whoever  makes  steam,  and  only  uses  a  proportion  of  it,  throws 
away  a  proportion  of  his  coal,  which  bears  a  relative  value  between  that  which 
is  generated  and  that  which  is  used.  This  engine  is  working  under  a  back 
pressure,  so  that  we  could  not  obtain  precisely  the  data  as  to  what  did  exhaust 
with  the  pressure  valve  lifted.  The  compression  upon  this  engine,  as  will  be 
seen  by  the  little  notch  upon  two  of  them,  is  considerable ;  so  much  so  that 
the  pressure  falls  back  before  the  valve  is  opened.  The  steam  line  falls  away 
rapidly  after  the  steam  is  admitted.  The  expansion  curve  is  very  good,  but 
no  doubt  the  valves  were  leaking  slightly,  and  perhaps  some  steam  was  blown 
by  the  piston.  These  matters  are  of  secondary  importance,  our  object  being 
to  instruct  our  readers,  rather  than  to  criticise,  except  so  far  that  our  readers 
shall  learn  to  read  the  diagrams  as  the  result  of  cause. 

Upon  the  right-hand  engine,  166  and  171,  the  compression  line  will  seem 
to  take  a  different  shape,  comparatively,  from  those  of  the  left-hand  engine, 


FIG.  25. 

the  admission  line  commencing  nearer  the  travel  of  the  valve  than  it  does 
upon  the  left-hand  engine,  so  that,  instead  of  forming  a  hook,  it  forms  a  point 
upon  one  side.  This  engine,  like  its  fellow,  shows  a  very  rapid  dropping  off 
of  steam  pressure  after  the  steam  valve  commences  to  open  to  admit  the 
steam,  and  the  piston  to  move  away.  This  would  raise  the  question  in  our 
mind  whether  the  supply  ports  were  large  enough  to  supply  that  volume  of 
cylinder  with  steam  ;  or,  as  is  the  case  with  most  slide  valves,  the  travel  is  so 
much  different  from  that  of  the  rotary  that,  in  order  to  be  enabled  to  cut  off, 
the  travel  is  short  and  the  ports  usually  somewhat  smaller  than  in  the  case  of 
valves  of  other  forms.  The  back  end  of  the  left-hand  engine  is  doing  much 
less  work  in  proportion  than  the  forward  end, — at  least  ten  per  cent,  differ- 
ence,—  doing  nearly  twenty  per  cent,  less  than  the  forward  end  of  the  right- 


52  TWENTY  YEARS    WITH  THE  INDICATOR. 

hand  engine.  At  the  same  time  the  steam  is  wire  drawn  worse,  or  it  falls  most 
in  pressure  after  being  admitted  to  the  cylinder.  Each  pair  are  given  as  they 
were  taken,  those  of  the  right-hand  engine,  and  those  of  the  left.  The 
difference  between  working  66  pounds  8.8  inches,  and  85  pounds  6.3  inches, 
amounts  to  28.2  per  cent.,  very  nearly,  as  the  8.8  inches  of  the  volume  of  the 
cylinder,  22  inches  in  diameter,  must  be  filled  with  steam,  every  stroke,  to  do 
the  amount  of  wrork  that  6.3  inches  in*  length  of  the  same  cylinder  would  do 
if  boiler  pressure  were  admitted  into  the  cylinder.  Aside  from  this,  the  card 
is  a  very  well  produced  one,  —  we  mean  aside  from  the  fact  of  falling  off  in 
boiler  pressure,  and  the  loss  of  effective  pressure  upon  the  head  of  the  piston 
after  the  steam -valve  opens.  These  diagrams  were  taken  by  the  writer  from 
the  engine,  and  are  a  peculiarity  of  the  type  or  figure  produced.  We  do  not 
know  of  the  economy  of  the  engine,  or  what  is  being  done  by  the  coal,  except 
that  it  cannot  be  economical  in  comparison. 


LESSON  XI. 

WE  have,  in  this  lesson  (Figs.  26,  27  and  28),  not  only  an  interesting,  but 
an  instructive  subject.  These  diagrams  were  taken  by  the  writer,  from 
machinery  designed  and  built  by  George  H.  Corliss,  to  the  order  of  the  Com- 
mittee of  Improved  Sewerage  of  the  City  of  Boston.  The  engine  is  a  double 
cylinder,  having  a  pair  of  beams,  a  cylinder  attached  to  one  end  of  each  l>eam, 


FIG.  26. 


and  the  other  end  of  the  beam  connected  with  a  crank  upon  the  fly-wheel 
shaft.  One  of  these  cylinders  carries  steam  at  high  pressure,  which  exhausts 
into  a  receiver.  The  receiver  extends  from  one  cylinder  to  the  other,  and 
supplies  the  low  pressure  cylinder.  The  diameter  of  the  high  pressure  cylin- 
der is  1 8  inches,  that  of  the  low  pressure  cylinder,  36  inches.  Both  cylinders 


TWENTY  YEARS    WITH  THE  INDICATOR.  53 

have  a  stroke  of  72  inches,  and  a  speed  of  about  27^  revolutions,  or  a  piston 
speed  of  330  feet.  The  pump  cylinders  are  connected  direct  to  the  walking 
beam,  half-way  between  the  trunnion  bearing  and  the  end  of  the  beam,  or  the 
point  at  which  the  steam  cylinder  connection  is  made  at  one  end,  and  the  crank 
connection  at  the  other,  —  therefore  the  speed  of  the  pump  plungers  per 
minute  is  165  feet  of  travel.  The  high  pressure  diagrams  are  taken  with  a  60 
spring,  by  the  Thompson  Indicator, 
built  by  the  American  Steam  Gauge 
Company;  the  low  pressure,  by 
the  same  Indicator,  with  a  20 
spring.  The  vacuum  gauge  showed 
27  inches.  The  steam  gauge  showed 
119  pounds,  of  which  112  pounds  is 
exerted  on  the  piston.  The  high 
pressure  cylinder  exhausts  under  a 
pressure  of  12  to  14  pounds,  n  to 
12  pounds  of  which  is  utilized  in  the 
low  pressure  cylinder.  The  instru- 
ments were  attached  to  the  engine 
about  two  o'clock  in  the  afternoon. 
The  engine  was  neither  stopped  nor 
adjusted  for  taking  diagrams.  The 
diagrams  were  taken  in  the  middle 
of  the  day's  work,  without  any  no- 
tice or  preparation,  and  were  not 
out  of  our  hands  from  the  time  we 
took  them  from  the  instruments 
until  they  went  to  the  engraver. 

This  engine  has  an  essentially 
new  arrangement  for  working  the 
valves.       It    has    no     compression 
whatever  upon  either  cylinder ;  the 
exhaust    shows    precisely   what    is 
going   on;    the  high  pressure  cyl- 
inder has  a  slightly  ragged  steam 
line;    but   the  point   of   cut  off  is 
very  sharply  defined,  and  the  line 
of  expansion  is  almost  theoretically 
perfect.     Another  point  is  particu- 
larly noticeable.     The  low  pressure  diagrams  do  not  vary  one  ten-thousandth 
of  one  inch  in  the  area  of  the  two  diagrams,  the  planimeter  reading  of  which 
is  given  upon  each  diagram.     The  high  pressure  end  varies  but  very  slightly 
when  we  come  to  consider  the  high  pressure  of  the  steam,  being  only  two  horse- 


54 


TWENTY  YEARS    WITH  THE  INDICATOR. 


power.     The  bottom  of  the  high  pressure  cylinder,  and  both  ends  of  the  low 
pressure  cylinder,  vary  less  than  one-fourth  of  one  horse-power. 

These  diagrams  were  taken  at  the  same  instant  of  time,  and  during  the 
same  strokes  of  the  engine.  The  outlines  of  the  cards,  aside  from  the 
serrations  in  the  steam  line,  are  very  perfect  indeed.  This  engine  is  jack- 
eted, and  has  produced  the  wonderful  result  of  1.37  pounds  of  coal  per 
indicated  and  developed  horse-power  per  hour,  using  poor  Cumberland  coal 
at  that.  The  actual  power  of  the  four  diagrams  averaged  is  235.73  horse- 
power. The  load  in  this  case  is  very  nearly  con- 
stant, and  consisted  in  lifting  water  to  a  height  of 
47.3  feet. 

The  reading  of  the  planimeter  and  the  horse- 
power are  both  given  upon  each  of  the  diagrams, 
and  it  will  be  an  interesting  study  for  those  who 
are  versed  in  the  use  of  steam,  or  those  who  are 
used  to  reading  the  Indicator  cards,  to  give  these 
some  attention.  Ninety-eight  per  cent,  of  the 
boiler  pressure  is  utilized  in  the  high  pressure 
cylinder,  and  from  95  to  97^  per  cent,  of  the 
receiver  pressure  is  utilized  in  the  low  pressure 
engine.  The  vacuum  attained  is  from  12%  to 
13  pounds,  and  the  temperature  was  not  below 
70°  F.  when  these  diagrams  were  taken.  The 
action  of  the  valves  may  be  noticed  particularly 
by  all  lovers  of  a  first-rate  diagram.  The  corners 
are  as  sharp  and  well  defined  as  it  is  possible  to 
make  them,  and  if  the  Indicator  had  not  been  an 
almost  completely  perfect  instrument  it  would  not 
have  shown  it  as  it  has.  The  vacuum  line  of  the 
low  pressure  engine  is  particularly  worthy  of  care- 
ful consideration.  The  condenser  takes  hold 
sharply  and  maintains  its  hold,  making  the  corner 
as  sharp  as  can  be.  This  is  a  truly  remarkable 
production.  The  lines  upon  the  high  pressure 
engine  show  as  perfect  a  working  of  steam  as  we 
ever  saw  from  any  engine,  while  the  production  of 
this  engine  in  duty  has  surpassed  that  of  any  other 
engine  ever  built,  and  tested  at  work,  so  far  as  we 
are  informed. 

Diagram  27  is  a  pump  card,  taken  directly  from  the  pump,  Thompson 
Indicator,  20  spring.  The  head  under  which  the  instrument  was  at  the  time 
was  47.3  feet.  The  dimension  of  the  pump  and  its  speed  are  given  above. 
The  pressure  upon  the  Indicator  is  that  due  to  a  head  of  water  of  that  height 


FIG.  28. 


TWENTY  YEARS    WITH  THE  INDICATOR.  55 

The  lines  of  the  card  indicate  that  the  pump  is  filled  and  kept  full  by  the  action 
of  the  piston  or  plunger.  This  card  will  also  bear  examination  and  compari- 
son, and  it  must  be  further  understood  that  this  engine  has  not  received  any 
special  elaboration,  but  was  built  and  running  five  months  and  three  days  from 
the  reception  of  the  order.  When  the  order  was  received,  no  drafts  or  pat- 
terns were  in  existence,  and  the  original  working  parts  of  the  engine  have 
never  been  tampered  with.  The  engine  was  not  assembled  until  it  was  put 
together  out  of  doors  ready  to  go  to  work,  in  such  a  position  that  it  could 
not  be  lined  or  leveled,  except  one  part  with  another.  The  bearings  for  the 
beams  to  work  on  are  54  feet  above  the  level  of  the  ground.  When  standing 
upon  the  gallery,  there  is  no  jar  or  shock  to  the  machine  in  its  working  at 
fiill  speed  and  under  its  full  load,  pumping  twenty-five  million  gallons  of 
water  47.3  feet  high.  The  performance  of  the  engine,  we  believe,  has  never 
been  equaled  in  the  world,  or  at  least  in  engineering  records. 

The  engine  is  at  work  at  the  Pettaconsett  works  of  the  Providence  Water 
Works,  with  a  set  of  pumps  entirely  different  from  those  which  it  was  working 
at  the  time  of  this  test.  The  pumps  which  were  first  used  were  adapted  and 
constructed  for  pumping  sewage,  while  the  pumps  which  are  now  in  operation 
are  of  the  same  general  construction,  although  different  in  shape,  as  those 
which  have  done  such  economical  work  in  the  Pawtucket  Water  Works,  and 
the  engine  which  was  guaranteed  by  Mr.  Corliss  to  develop  100,000,000  duty, 
kas  shown  +  ii3,cxx>,ooo  in  its  test  by  the  city  engineer  of  Providence. 


LESSON  XII. 


THE  educated  man,  —  educated,  we  mean,  in  practice,  —  and  the  practical 
engineer  will  see,  in  examining  the  diagrams  in  this  lesson  (Figs.  29  and  30), 
two  of  the  most  elegantly  perfect  steam  engine  diagrams  that  they  have 
ever  laid  eyes  upon.  These  diagrams  were  taken  from  the  Pawtucket  (R.  I.) 
Water  Works  pumping  engine,  built  by  George  H.  Corliss,  and  which,  up  to 
the  time  of  the  construction  of  the  Boston  sewage  pumping  engine,  by  Mr. 
Corliss,  had  accomplished  the  largest  duty  in  the  lifting  of  water  that  had  ever 
been  attained  by  any  engine  in  actual  operation,  in  a  practical  way,  under 
the  control  and  daily  management  of  the  engineer  in  charge. 


56  TWENTY   YEARS    WITH  THE  INDICATOR. 

A  description  of  this  engine  will  not  be  out  of  place.  It  is  a  compound 
engine  of  the  horizontal  pattern.  The  high  pressure  cylinder,  15  inches  in 
diameter,  30  inches  stroke ;  the  low  pressure  cylinder,  30  inches  diameter,  30 
inches  stroke.  The  pumps  are  in  a  hollow  casting,  which  serve  also  for  a 
pillow-block  for  the  fly-wheel,  which  is  mounted  between  the  cylinders.  The 
pump  is  in  the  lower  part  of  this  pillow-block  casting,  and  is  attached  directly 
to  the  same  rod  that  the  piston  is.  The  slides  are  in  the  rear  of  the  pillow- 
block,  where  it  is  connected  with  a  peculiar  rocker-motion,  which  is  again  con- 
nected to  the  crank  upon  the  fly-wheel  shaft  upon  either  side  of  the  engine. 
The  diameter  of  the  pump  barrel  is  15  inches,  the  diameter  of  the  plunger  is 
10.52  inches.  The  diameter  of  the  air-pump  is  20  inches,  length  of  stroke  7^ 
inches.  The  suction  and  discharge  pipes  are  15  inches  in  diameter;  the  fly- 
wheel is  1 8  inches  in  diameter.  Three  boilers  are  used,  14  feet  high,  4  feet  in 
diameter,  48  tubes  three  inches  in  diameter,  the  fire-chamber  being  40  inches 
high.  The  grate  surface  is  19.63  square  feet,  the  fire  surface  560  square  feet, 
the  average  steam  space  3^  to  4  feet,  —  it  is  supposed  that  the  steam  space 


FIG.  29. 

means  3^  feet  to  4  feet  in  height,  of  the  boiler,  —  the  steam  pressure,  125 
pounds ;  average  water  pressure,  no  pounds ;  the  head  against  the  pump  is 
269.1  feet;  displacement  at  one  revolution,  5.6592  square  feet.  The  test  of 
this  engine  for  twelve  days,  running  ten  hours,  and  lying  still  fourteen  hours, 
gave  104,357,654  foot  pounds  for  every  one  hundred  pounds  of  coal.  This 
trial  was  made  on  August  6th,  and  the  days  following,  in  1878.  The  engine 
was  started  pumping  February  2d,  1878,  pumping  directly  into  the  pipes  until 
November  6th,  1878.  After  it  was  put  in  charge  of  the  engineer,  the  duty  for 
the  first  year  was  106,234,300  foot  pounds  on  all  fuel  consumed  in  pumping. 

One  diagram  shown  is  from  the  high  pressure  cylinder,  15  inches  in 
diameter,  30  inches  stroke,  46  revolutions  per  minute,  steam  at  125  pounds, 
scale  58.  There  is  only  one  criticism  to  make  upon  this  diagram.  It  is  abso- 


TWENTY  YEARS    WITH  THE  INDICATOR.  57 

lutely  perfect.  Taking  the  clearance  of  the  engine,  the  expansion  curve  is  so 
nearly  perfect  that  it  is  no  use  to  express  it  in  any  other  way.  The  steam  line, 
as  well  as  tne  admission  line,  are  almost  geometrical  forms.  The  expansion 
curve  in  this  card  is  slightly  better  than  that  of  the  engine  built  for  the  Boston 
Sewage  Committee,  mentioned  in  the  preceding  lesson,  and  the  reason  for  this 
may  be  found  in  the  fact,  probably,  that  the  engine  makes  46  strokes  instead 
of  27^.  The  other  diagram  is  from  the  low  pressure  cylinder  of  the  same 
engine,  30  inches  diameter,  30  inches  stroke.  The  pressure  from  the  high 
pressure  cylinder  is  almost  entirely  utilized  in  the  low  pressure.  The  vacuum 
is  as  good  as  it  can  be  in  practice,  approaching  the  theoretical  very  closely. 
The  condenser  takes  full  hold  very  early  in  the  stroke,  and  maintains  an  ele- 
gant vacuum  line  until  the  valve  closes.  The  difference  between  the  high 
pressure  cylinder,  and  that  of  the  imitators  of  Mr.  Corliss  is,  that  they  cannot 
obtain  a  steam  line  which  amounts  to  boiler  pressure.  In  this  case,  nearly  the 
entire  boiler  pressure  is  secured  by  the  piston.  The  steam  line  falls  one  pound 


FIG.  30. 

before  it  is  cut  off.  These  diagrams  were  taken  without  any  preparation.  The 
coal  consumption  was  1.8  pounds  per  horse-power  per  hour,  and  there  have 
been  no  repairs  on  the  engine  since  it  was  started.  It  had  done  over  five 
years'  work,  of  ten  hours  per  day,  at  the  time  the  diagrams  were  taken. 

We  have  seen  and  taken  thousands  of  diagrams  in  actual  practice,  and  we 
have  yet  to  see  one  that  approximates  these  in  absolutely  answering  every 
requirement  of  the  engineer,  and  we  believe  it  will  be  a  long  time  before  we 
see  another.  The  record  of  the  engine  has  been  that  of  a  perfect  working 
machine,  furnished  within  the  time  it  was  promised,  at  the  price  at  which  it 
was  engaged,  and  instead  of  doing  30  per  cent,  of  the  work  that  it  was  con- 
tracted for,  it  did  over  30  per  cent,  more  work  than  Mr.  Corliss  guaranteed  it 
to  do. 

Diagrams  may  be  taken  almost  absolutely  perfect,  and  if  engineers  who 
study  these  lessons  with  an  eye  to  benefit  themselves,  can  produce  such  dia- 


58  TWENTY  YEARS    WITH  THE  INDICATOR. 

grams  upon  their  cylinders  in  actual  working,  as  that  of  the  high  pi  essure 
cylinder,  they  will  not  have  to  figure  very  largely  upon  coal ;  and  when  their 
engine  is  in  condition  to  make  these,  they  need  not  fear  extensive  bilk  for 
repairs. 


LESSON  XIII. 

IN  this  lesson  we  have,  for  the  moment,  abandoned  actual  practice  in 
reading,  for  the  best  effect,  and  show  matters  which  are  occasionally  found  in 
actual  practice.  Fig.  31  is  a  card  taken  from  a  Corliss  engine,  20^6  inches 
diameter,  four  feet  stroke,  60  revolutions,  72  pounds  boiler  pressure,  30  spring. 
This  engine  has  received  a  great  deal  of  attention  from  a  number  of  parties. 
There  was  known  to  be  a  fault  existing,  and  yet  the  fault  was  not  traced,  and 


FIG.  31. 

the  trouble  was  not  remedied.  The  expansion  line  seems  to  be  good,  and  the 
atmospheric  and  exhaust  lines  fairly  run  into  each  other,  so  that  no  troubk 
could  exist  in  that  region.  There  is  no  compression,  but  there  is  a  curious 
hump  at  A,  which  might  occur  from  one  of  two  things,  but  in  this  case  it  was 
an  anomaly.  The  cylinder  head  was  taken  off,  and  the  full  pressure  of  steam 
on  the  steam  valve  showed  that  the  valve  did  not  leak ;  consequently  it  was 
not  a  leaky  steam  valve.  The  question  then  arose,  Where  was  the  trouble  ? 


TWENTY  YEARS   WITH  THE  INDICATOR.  59 

The  engine  was  started  again  and,  as  we  have  stated,  several  engineers  gave 
up  the  problem,  declaring  that  the  engine  was  not  properly  constructed.  Mr. 
Mosman  (now  deceased),  with  the  American  Steam  Gauge  Company,  was  sent 
to  examine  the  engine,  and  it  was  a  considerable  problem  to  him,  as  well  as 
tedious.  He  made  all  the  ordinary  tests,  found  the  valves  tight,  and  then 
began  to  use  his  judgment.  Upon  experimenting  with  the  exhaust  valve  in 
this  end  of  the  machine,  it  was  found,  after  the  engine  had  moved  an  inch 
or  two  of  the  stroke,  that  the  exhaust  valve  had  been  set  so  that  it  opened 
upon  the  back  side,  and  allowed  the  steam,  or  a  portion  of  it  at  least,  for  two 
or  three  inches  of  the  stroke,  to  pass  by.  This  was  corrected,  and  the  trouble 
was  at  an  end.  And  yet  there  are  two  or  three  engineers  who  declare  that  the 
engine  is  not  right,  and  cannot  be  made  right,  although  it  makes  as  handsome 
a  diagram  as  any  Corliss  engine  that  has  been  in  use,  and  been  taken  good 
care  of.  1 1  was  a  very  serious  defect,  and  it  was  a  puzzle. 


FIG.  32. 

Fig.  32  represents  a  not  uncommonly  found  result.  ,  In  this  case  the 
engine  gets  blamed  for  what  the  Indicator  is  at  fault  about.  And  yet  the  Indi- 
cator, with  which  this  was  taken,  was  in  the  hands  of  an  expert.  The  cut  off 
is  very  near  the  point,  A,  and  the  dotted  line,  and  would  extend  above  the 
line  as  shown  by  the  dotted  line,  but  in  this  case  the  instrument  leaks,  the 
piston  and  the  cylinder  both  being  worn,  —  we  mean  the  piston  and  cylinder  of 
the  Indicator,  —  hence,  in  this  case,  the  Indicator  is  very  unreliable.  This  can 
be  ascertained  fully  by  actual  tests,  and  whoever  reads  this  diagram,  and  is 
posted  in  his  business,  would  find,  upon  applying  the  expansion  curve,  that 
the  point  of  cut  off  was  very  much  shorter  than  that  shown  in  the  card.  This 
case  was  also  handed  over  to  our  friend  Mosman,  and  the  Indicator  was  after- 
wards reorganized. 

Fig.  33  is  another  case  of  a  most  peculiar  diagram.  The  admission  line  is 
straight,  the  engine  taking  steam  like  a  hurricane,  but  the  piston  Indicator 
drops  from  the  point,  A,  to  that  of  B,  in  precisely  the  same  way  that  it  comes 


6o  TWENTY  YEARS    WITH  THE  INDICATOR. 

up  on  the  admission  line.  This  line  is  not  due  to  the  action  of  the  engine,  but 
the  piston,  or  the  cylinder,  or  both,  were  grooved,  the  steam  being  shot  into 
it,  the  piston  moving  at  a  good  speed.  When  the  Indicator  commences  to 
descend,  it  goes  out  of  all  semblance  of  real  expansion,  because  the  steam 
shoots  through  the  grooves  until  it  partially  seats  itself  again,  when  the  vibra- 
tion makes  the  little  notch  in  the  expansion  line.  All  these  are  matters  which 
can  only  be  learned  by  practical  demonstration,  and  this  is  a  most  peculiar 
case,  yet  it  is  not  the  only  one  we  have  ever  seen.  An  Indicator,  to  be  relia- 
ble, must  have  a  considerable  amount  of  attention  paid  to  it.  The  engineer 
must  know  how  to  apply  tests  for  correctness,  and  he  must  know  how  to  read 
the  lines  which  he  gets,  and  know  what  is  possible  to  be  made  by  his  careless- 
ness, or  lack  of  attention,  in  applying  his  motion,  as  well  as  in  seeing  that  his 
instrument  is  in  perfect  order. 

The  effect  of  either  one  of  the  illustrations  which  we  have  given,  if  a  man 
were  ignorant  at  all  of  the  true  reading  of  the  lines,  would  be  to  go  on  with 


FIG.  33. 

poor  work,  condemning  the  engine  for  what,  in  two  of  the  cases,  is  clearly  the 
fault  of  the  instrument,  and,  in  Fig.  31,  a  lack  of  brains  in  whoever  attempted 
any  such  mal-adjustment ;  but  there  are  certain  engineers  who  run  by  the  rule 
of  thumb,  and  it  proves  a  very  expensive  rule  to  run  by  for  the  man  who  pays 
for  the  coal.  If  a  man  has  no  care  for  the  interests  of  his  employers,  he  is  the 
last  man  in  the  world  to  have  the  handling  of  an  Indicator  or  the  running  of 
a  steam  engine. 

These  three  illustrations  make  one  of  the  most  interesting  lessons  which  we 
have  given.  They  are  from  positive  fact,  in  actual  practice.  In  every  case  the 
information  which  they  embody  has  been  most  dearly  bought  by  the  parties 
who  were  paying  for  the  fuel  which  was  run  through  the  engines  in  question. 


TWENTY   YEARS    WITH   THE  INDICATOR.  61 

If  an  engineer  will  pay  attention  to  these  lines,  and  remember  how  they  can 
be  caused,  he  will  then,  whenever  a  difficult  or  seemingly  uncommon  card  is 
presented  for  him  to  read,  remember,  from  his  own  experience,  or  from  his 
reading,  —  if  he  observes  and  remembers,  —  that  certain  matters  will  cause 
certain  results,  and  he  will  be  enabled  to  judge  of  the  probability  of  these 
without  experimenting  at  the  expense  of  his  employer.  A  man  to  be 
successful  with  the  Indicator  must  be  one  who  reasons,  and  applies  the 
somewhat  uncommon  rule  of  common  sense ;  and  the  man  who  has  the  most 
common  sense  is  the  man  who  oftenest  succeeds  in  obtaining  excellent  results 
from  the  proper  use  of  his  instrument. 


LESSON   XIV. 


IT  is  frequently  stated  that  the  Indicator  is  of  very  little  use,  except  for 
the  careful  noting  of  results,  or  for  the  following  out  of  doctrines  or  theories 
which  relate,  more  particularly,  to  expert  tests.  This  assertion  is  as  void  of 
truth,  and  is  as  far  from  the  fact,  as  it  is  possible  to  put  any  given  number  of 
words  into  a  sentence  attempting  to  mean  something,  and  yet  make  a  signal 
failure  of  it. 

Fig.  34  is  a  curious  figure  to  be  described  by  an  instrument.  This  was 
taken  from  a  250  horse-power  engine,  made  by  Charles  S.  Brown,  of  Fitch- 
burg,  but  Mr.  Brown,  in  his  adjustment  of  the  engine,  did  not  make  any  such 
card  as  this.  One  of  those  men  who  know  everything  but  one,  and  who  never 
use  the  Indicator,  —  a  man  who  was  able  to  set  the  valves  of  an  engine  by  the 
marks,  or  by  gauges,  or  measures,  or  by  guess,  or  something  else,  —  made  his 
arrangemenents  upon  this  engine,  and  when  he  got  the  machine  in  such  a 
condition  that  it  would  not  run  with  much  more  than  half  its  usual  load,  he 
concluded  that  the  engine  was  not  worth  anything ;  and  the  owners  of  the 


62  TWENTY  YEARS    WITH  THE  INDICATOR. 

engine  concluded  that  they  must  find  somebody  who  could  tell  tnem  whether 
the  engine  was  good,  bad,  or  indifferent.  The  diagram  in  question  was  one 
of  the  first  ones  taken  after  the  adjustment  of  the  instrument,  and  it  fully  illus- 
trates the  folly — or  foolishness,  to  use  a  plainer  word — of  a  man  in  attempting 
to  tinker  with  the  valves  of  an  engine.  In  this  case  the  exhaust  valve  closes 
at  A,  while  the  stroke  ends  at  B.  Compression  takes  place,  which  carries 
the  piston  of  the  Indicator  to  C,  when  it  follows  the  outer  line  back  to  D,  as 
the  piston  starts  on  its  return  stroke.  At  this  point,  rather  late  in  the  day,  the 
steam  valve  opens  ;  but,  as  a  stern  chase  is  always  a  long  one,  the  engine  gets 
steam  all  the  way,  from  D  to  E,  as  the  motion  of  the 
piston  is  shown  by  the  leaning  line  from  D  to  E,  and 
the  pressure  cannot  be  brought  up  fully,  because 
the  piston  is  moving,  and  requires  a  very  large 
amount  of  steam,  in  order  to  fill  the  volume  of  the 
cylinder  from  B  to  D,  which  could  not  be  filled  until 
after  the  valve  opened  at  D.  From  E  to  F,  the  steam 
line  is  short,  where  the  cut  off  takes  place.  The  ex- 
pansion line  is  eood.  the  exhaust  line  is  first-rate,  but 
the  line,  E,  G,  B,  D,  C,  simply  represents  lost  work 
or  steam  used  after  it  could  be  useful,  or  of  any  effect. 
The  area  of  these  figures  is  respectively  194  effective, 
and  70  absolutely  lost  or  thrown  away.  Undoubt- 
edly, if  the  steam  had  been  properly  applied,  210  to 
220  would  have  expressed  the  whole  area ;  but,  in  this 
case,  one-third  of  the  steam  used  is  absolutely  thrown 
away.  This  is  an  interesting  study  to  show  what  can 
be  done  by  these  men, — and  we  believe  there  are  less 
of  them  than  ten  years  ago,  —  who  can  set  an  engine 
by  their  ear,  or  by  marks,  and  it  will  be  a  caution  to 
those  among  our  readers  who  have  the  good  sense  to 
let  alone  matters  which  they  cannot  be  positively  sure 
of.  After  the  engine  was  properly  adjusted,  there  was 
no  more  doubt  as  to  whether  Mr.  Brown's  work  was 
or  was  not  up  to  his  ordinary  standard. 

Fig.  35  represents,  truthfully,  only  the  proportion 
that  is  being  done  by  the  different  ends  of  the  engine. 
The  little  hooks  at  A,  and  the  badly  formed  lines,  B, 
are  due  to  the  inferiority  of  the  instrument,  which 
was  in  very  bad  order.  In  this  case  the  instrument 
leaked.  When  the  compression  was  made,  before 

the  valve  opened,  the  steam  came  through  the  instrument  to  a  certain  extent 
so  that  the  piston,  by  the  action  of  the  spring,  dropped,  making  this  hook. 
There  is  no  point  of  cut  off  upon  the  one.  Upon  the  other,  the  cut  off  if 


TWENTY   YEARS    WITH  THE  INDICATOR.  63 

squarer,  but,  at  the  same  time,  it  falls  like  a  brick.     Very  little  need  be  said  of 
these  diagrams,   except  to  show  that  an  instrument,  which  is  not  properly 


FIG.  35. 


adjusted,  or  which  is  not  as  it  should  be,  may  mislead  a  man  very  seriously  in 
getting  at  the  effective  value  of  the  work  being  produced. 


LESSON  XV. 


THE  diagrams  in  the  present  lesson  are  of  more  than  passing  interest,  and 
were  taken  from  the  engine  of  a  man  who  places  no  value  on  the  Indicator. 
It  is  only  necessary  to  say  that  the  diagrams  were  only  taken  when  he  found 
that  something  was  the  matter,  which  his  engineer  could  not  manage;  and 
this  is  only  one  of  numerous  practical  applications  of  the  value  of  the  Indi- 
cator, which  the  expert  in  its  use  is  continually  meeting.  The  engine  in 
question  is  a  Harris-Corliss,  14  inches  diameter  of  cylinder,  42  inches  length 
of  stroke,  60  revolutions  per  minute,  the  pressure  in  the  boiler  varying  from 
65  to  75  pounds.  The  diagrams,  Figs.  36  and  37,  are  from  the  different  ends 
of  the  engine,  37  being  the  crank  end,  and  36  the  head  end.  Fig.  37  is  one  of 
those  peculiar  looking  ones  which  we  frequently  meet  with  in  actual  practice, 
more  especially  from  engineers  who  know  exactly  how  to  set  their  valves  by  a 
scratch  or  prick  punch  mark;  and  they  can  tell  exactly  how  "she  takes 
steam  "  by  watching  the  cut-off  slide.  The  engineer,  in  this  case,  simply  had 
to  give  it  up,  and  if  he  had  gone  a  few  steps  further,  his  engine  would  have 
run  the  other  way.  Fig.  36  shows  three  lines,  as  they  were  taken  from 


64  TWENTY  YEARS    WITH  THE  INDICATOR. 

the  instrument,  and  they  are  most  wretchedly  irregular  lines  too.  The  steam 
line  is  as  full  of  humps  as  a  camel's  back,  and  the  notches  and  irregularities 
are  the  exact  counterpart  of  the  movements  or  action  of  the  steam,  as  it  is 
admitted  to  the  cylinder.  The  admission  line,  in  itself,  is  very  late.  The 
steam  valve  commences  to  open  only  after  the  piston  has  commenced  its 
stroke.  It  does  not  open  fully  until  after  the  piston  has  traveled  several 

inches.  The  exhaust  will  be  seen  to  be  very  late, 
upon  both  diagrams,  Figs.  36  and  37.  It  is  com- 
paratively small  in  its  showing  upon  Fig.  36,  from 
the  fact  that  it  shows  a  very  much  lighter  load 
than  that  of  Fig.  37.  The  amount  of  power, — 
32.4  horse-power,  —  given  on  Fig.  36,  is  the 
mean  of  three  lines,  the  largest  amount  being 
plus  50  and  the  smallest  only  22.  Fig.  37 
has  the  same  general  outline  as  Fig.  36,  but 
in  this  case  Fig.  36  was  set  to  cut  off  at  less 
distance  than  Fig.  37,  so  that  Fig.  37  is  only 
a  single  line,  and  is  doing  three-quarters  the 
work  of  the  engine.  The  line,  in  the  case  of 
Fig.  37,  is  very  bad  indeed.  The  valve  does  not 
commence  to  open  until  after  the  piston  has 
started  on  its  return  stroke.  The  cut  off  is  very 
badly  defined,  and  might  lead  to  the  idea  that  the 
valves  were  leaking  badly,  but  no  experienced 
engineer  would  try  to  ascertain  this  question 
until  the  valves  were  in  proper  position.  The 
toe  at  the  end  of  the  expansion,  at  the  commence- 
ment of  the  exhaust  line,  is  an  additional  amount 
of  work  thrown  away. 

This  is  only  a  fair  specimen  of  the  way  that 
many  engineers  get  their  valves,  and  they  are 
always  found  in  the  hands  of  those  people  who 
do  not  use  the  Indicator,  and  who  frequently 
make  the  assertion  that  they  do  not  believe  in  the 
Indicator,  for  it  is  of  no  use.  All  such  are  per- 
fectly welcome  to  their  belief,  and  their  employers 
FIG-  36'  sometimes  change  their  minds  when  the  engine 

has  been  properly  indicated  and  adjusted  by  those  who  do  believe  in  the 
Indicator,  and  who  know  how  to  apply  it  and  read  properly  its  results. 

C  and  D  (Fig.  38)  are  from  the  very  same  engine,  after  the  Indicator  had 
been  properly  applied,  and  the  needed  corrections  made  in  the  motion  of  the 
valves.  The  horse-power  is  almost  identically  the  same  in  both,  the  fractions 
being  very  small.  The  compression  is,  almost  to  a  unit,  the  same.  The 


TWENTY   YEARS    WITH  THE  INDICA  TOR.  65 

admission  line  is  lost  in  the  proper  compression,  and  the  steam  line  is  carried 
as  straight  as  a  line  can  be.  The  line  of  expansion  shows  very  little  loss,  and 
the  diagram,  taken  altogether,  is  a  very  good  production.  It  is  needless  to 
say  that  a  very  considerable  saving  of  fuel  resulted  as  the  difference  between 
the  engineer's  setting,  Figs.  36  and  37,  and  the  man  who  applied  the  Indi- 
cator in  Fig.  38.  These  diagrams  are  from  actual  practice,  and  were  given  us 


FIG.  37.  FIG.  38. 

by  the  late  Mr.  Mosman,  of  the  American  Steam  Gauge  Company.  They 
were  taken  with  40  springs,  and  the  engine  at  its  regular  work.  Probably  the 
question  never  entered  the  head  of  the  engineer  in  charge,  as  to  the  result  of 
the  use  of  steam,  as  in  the  diagrams,  Figs.  36  and  37.  The  steam  in  Fig.  36  is 
admitted,  in  all  sorts  of  quantity,  in  the  endeavor  of  the  regulator  to  reach 
after  and  equalize  the  load,  which  is  done  in  the  other  end  of  the  cvlinder;  but 


66  TWENTY  YEARS    WITH  THE  INDICATOR. 

as  the  cut-off  slides  are  set,  in  Fig.  38,  to  cut  off  longer  than  is  necessary,  and  in 
Fig.  36  are  set  shorter  than  they  should  be,  it  is  simply  impossible  for  the  regu- 
lator to  adjust  the  difference  between  them  ;  for  the  difference  is  so  great  that 
the  regulator  cannot  measure  it  by  the  differential  strokes  of  the  cut-off  slides, 
or  the  motion  which  is  given  them  through  the  change  of  position  of  the  balls 
on  the  governor.  In  this  case  the  crank  end  of  the  engine  is  doing  more  than 
double  that  of  the  head  end,  and  these  motions  of  the  head  end  are  shown  in 
the  irregular  steam  lines  by  its  race  after  the  other  end  of  the  engine ;  and 
exactly  in  proportion  as  these  lines  differ  from  each  other  was  the  resistance 
or  the  strain  upon  the  different  parts  of  the  engine,  differing  at  each  end  of  the 
stroke,  making  120  times  per  minute.  In  other  words,  the  engine  jumps  120 
times  a  minute  after  its  load,  and  the  regulator  is  simply  unable  to  adjust  the 
difference;  or,  in  other  words,  is  attempting  to  accomplish  an  impossibility. 
The  engine  in  this  case  is  using  something  like  forty  per  cent,  or  more  steam 
than  would  be  necessary,  when  properly  adjusted,  as  is  seen  in  Figs.  37 
and  38.  This  is  only  another  important  lesson  that  people  can  learn  if  they 
will,  but  usually  only  learn  when  they  are  obliged  to.  It  is  all  the  more  to  the 
credit  of  the  Indicator  that  it  is  able  to  show  up,  in  the  hands  of  an  experienced 
manipulator,  these  points  where  pocket  value  is  the  result  attained ;  and  in  a 
case  like  this,  the  amount  of  coal  burned,  before  and  after  adjustment,  is  a 
factor  that  can  always  be  measured  in  dollars  and  cents.  This  is  the  standard 
of  too  many  steam  users  in  quite  an  opposite  direction. 


LESSON   XVI. 


IN  this  lesson  we  have  a  decided  difference  in  engineering  practice,  and 
upon  one  of  the  points  which  we  have  dwelt  in  previous  lessons,  and  which 
will  be  distinctly  exemplified  by  the  comparison  between  the  cards.  It  refers 
to  the  realization  of  the  boiler  pressure  of  the  cylinder.  The  diagrams,  A,  B 
(Fig.  39),  were  sent  us  by  a  correspondent,  with  the  following  data :  Buckeye 
engine,  14  X  28,  40  scale,  70  pounds  steam,  112  revolutions.  Diagrams  taken 
with  one  instrument  standing  in  the  middle  of  the  cylinder, — which,  we  suppose, 
means  taken  with  a  three-way  cock.  A  is  the  crank  end  of  the  engine ;  B  is 
the  head  end.  The  figures  102  and  116  represent  respectively  the  area  of  the 


TWENTY  YEARS   WITH  THE  INDICATOR.  67 

diagram,  as  measured  by  the  planimeter.  C,  C,  represents,  by  the  little  white 
line  above  the  letter,  the  70  pounds  boiler  pressure.  D  represents  the  atmos- 
pheric line  of  the  instrument.  Our  correspondent  writes  :  "  My  vacuum  gauge 
reads  25  inches,  while  the  vacuum  on  the  instrument  only  shows  four  pounds, 
or  eight  inches."  He  further  writes  :  "  Will  you  please  give  me  some  informa- 
tion in  regard  to  setting  the  valves  ?  " 

We  cannot  give  any  information  regarding  the  setting  of  the  valves  from 
the  diagrams  given.  The  engine  appears  to  be  working  free,  and  really  it  is 
the  best  pair  of  Buckeye  diagrams  we  ever  saw  taken  from  actual  practice, — we 
mean  the  outline  and  apparent  action  of  the  valve.  In  taking  diagrams  with 
the  three-way  cock,  where  there  is  any  variation  in  the  load,  it  is  absolutely 
impossible  to  balance,  as  we  term  it,  each  end  of  the  cylinder,  and  have  one  do 
the  same  amount  of  work  as  the  other  on  its  return  stroke.  If  both  of  these 
diagrams  had  been  taken  upon  the  same  stroke  of  the  engine,  with  two  instru- 
ments, one  upon  either  end,  we  should  say,  by  all  odds,  to  set  the  valve  so 


FIG.  39. 

that  the  crank  would  not  be  cut  off  quite  so  soon.  The  particular  feature 
about  these  cards  is  one  which  we  generally  find  on  this  kind  of  an  engine  — 
it  fails  to  utilize  the  full  amount  of  the  boiler  pressure.  In  another  set  of  cards, 
sent  by  the  same  party,  from  the  same  engine,  and  doing  much  more  load,  the 
head  end  measures  227,  and  the  crank  end  194  on  the  planimeter.  In  this 
case,  quite  a  considerable  difference  is  therefore  indicated  in  horse-power,  the 
head  end,  as  is  generally  the  case,  doing  the  most  work.  Taking  the  pressure 
of  the  steam  and  the  point  of  cut  off,  this  diagram  approaches  the  theoretical 
curve  in  a  very  practical  degree. 

The  diagrams,  C,  D  (Fig.  40),  were  taken  from  a  Harris -Corliss  engine, 
36  X  14  inches,  in  the  Massachusetts  Charitable  Mechanic  Association  build- 
ing, at  the  exhibition  of  1881 ;  75  revolutions,  40  spring,  boiler  pressure  85 
pounds, — the  steam  was  carried  some  distance, — gauge  on  the  pipe  82  pounds. 
The  Thompson  Indicator  was  applied  by  Mr.  Mosman  for  the  American  Steam 


68 


TWENTY  YEARS    WITH  THE  INDICATOR. 


Gauge  Company.  The  initial  pressure,  as  the  Indicator  records  it,  is  78.5 
pounds.  These  diagrams  were  taken  by  a  three-way  cock,  but  under  radically 
different  circumstances  from  those  which  are  shown  by  the  diagram  in  Fig. 
40.  The  engine  had  no  connection  with  any  machinery  in  the  building, 
except  the  dynamo  machines  for  the  electric  lights.  The  engine  regulated  in 
the  very  best  possible  manner,  the  variation  in  speed  was  almost  nothing,  being 
run,  therefore,  with  as  constant  a  load  as  it  was  possible  to  attach  to  it,  diagrams 
being  taken  by  turning  the  cock.  Probably  one  was  taken  upon  one  stroke  of 
the  engine,  and  the  other  not  missing  more  than  one  or  two  strokes,  while  the 
load,  at  the  same  time,  is  shown  by  twelve  pairs  of  diagrams,  which  we  have, 
and  which  varied  much  less  than  one  horse-power  in  twelve  sets.  One  end 
reads  420  on  the  planimeter,  and  the  other  417.  This  is  a  result  that  is  very 
seldom  obtained  in  practice,  and  in  this  case  it  was  undoubtedly  effected  by 
good  judgment  and  careful  adjustment  by  the  parties  in  charge  of  the  engine. 


C  D/ 

\          MP   87. 1 96        / 


FIG.  40. 

In  this  case  it  will  be  seen  that  almost  ninety-six  per  cent,  of  the  steam  pipe 
pressure  is  actually  shown  by  the  piston  of  the  Indicator  and  its  pencil  attach- 
ment. Two  cases  could  hardly  show  more  completely  the  difference  in  the 
practice  of  two  engine  builders.  The  Harris-Corliss  engine  was  making  450 
feet  piston  speed  per  minute.  This  result  shows  that  the  Indicator  is  reliable, 
when  in  practical  hands,  to  a  nicety  that  was  hardly  credited  to  it  a  few  years 
since,  even  by  men  of  experience  and  who  should  have  had  confidence  in  their 
own  opinions.  And  yet  there  are  men  who  call  themselves  engineers,  who 
attempt  to  belittle  the  results  of  the  Indicator's  reading,  or  practical  applica- 
tion. But  one  thing  is  certain  —  engine  builders  are  coming  to  place  more 
and  more  reliance  upon  the  application  of  the  Indicator  in  practical  hands ; 
and  a  man  who  has  any  breadth  of  practice  with  the  Indicator  can  demonstrate 
to  the  absolute  satisfaction  of  any  party  who  knows  enough  to  know  the 
difference  between  twelve  tons  of  coal  a  day  and  fifteen  tons  of  coal  a  day,  that 
the  man  who  sets  by  marks  or  spots,  prick  punches,  or  the  end  of  his 


TWENTY   YEARS    WITH  THE  INDICATOR  69 

thumb,  may  work  a  week  upon  an  engine  in  setting  the  valves,  and  the  prac- 
tical application  of  the  Indicator  will  demonstrate  that  in  this  way  the  valves 
of  any  good  engine  could  not  be  set  within  a  row  of  apple  trees  of  right,  and 
apple  trees  are  usually  not  nearer  than  twenty  feet  apart. 


LESSON   XVII. 


THE  cards  in  this  lesson  are  from  actual  practice,  by  an  engineer  who 
seems  to  know  something  about  the  Indicator,  and  that  it  is  something  more 
than  a  curiosity  or  a  plaything.  They  were  sent  us  by  a  correspondent,  who 
asked  several  questions.  Fig.  41  is  a  diagram  from  a  modern  built  engine,  with 
so-called  Greene  cut-off.  The  party  running  this  engine  supposed  he  had 
arrived  at  the  limit  of  its  power.  After  the  valves  had  been  adjusted,  twenty 
pounds  less  boiler  pressure  were  used,  with  a  very  great  saving  in  fuel.  The 
size  of  this  engine  is  12  inches  diameter,  36  inches  stroke,  50  revolutions  per 
minute,  boiler  pressure  55  pounds,  scale  40.  Our  correspondent  stated  that 
the  valves  were  left,  by  the  man  who-  put  them  in,  so  that  they  produced  this 
diagram.  This  is  rather  a  curious  looking  figure,  yet,  by  no  means,  an 
uncommon  one.  B  shows  the  boiler  pressure,  and  what  would  have  been  the 
admission  line,  if  the  valves  had  been  in  order.  The  valves  do  not  fully  open, 
so  as  to  admit  any  approximation  to  the  boiler  pressure,  until  after  the  piston 
has  traveled  more  than  one-fifth  of  its  stroke.  We  should  judge  from  its 
length,  after  it  gets  a  steam  line,  that  the  engine  was  heavily  loaded  for  its 
capacity,  although  little  can  be  told  as  to  the  load  which  the  engine  is  really 
doing  from  such  an  outrageous  outline  as  this.  The  steam  is  carried  for  a 
large  proportion  of  the  stroke,  the  expansion  line  is  irregular,  the  exhaust 
valve  only  partially  opens  at  C,  while,  if  it  opened  as  it  should,  it  would  com- 
mence at  D,  and  make  the  line,  D,  E.  In  this  case  the  exhaust,  valve  really 
opens  at  C,  and  the  piston  returns  some  distance  before  the  steam  is  freely 
exhausted.  For  some  reason — we  cannot  see  why — there  seems  to  be  a  small 
amount  of  compressed  steam  at  E.  When  the  piston  starts  upon  its  return 
stroke,  the  piston  of  the  Indicator  drops,  and  the  under  portion  of  the  loop  is 


TWENTY   YEARS    WITH  THE  INDICATOR. 


formed.  After  the  piston  has  returned  upon  its  stroke,  and  the  lines  cross 
each  other,  the  steam  valve  seems  to  open  but  slightly,  and  the  admission  line 
commences  at  F.  The  engine  works  under  a  small  amount  of  back  pressure, 

and  makes  a  very  poor  use  of  the  steam  which 
is  fed  to  it  from  the  boiler ;  and  if  our  correspon- 
dent had  sent  us  a  card  showing  the  engine  cor- 
rectly working  with  approximately  the  same  load 
and  the  same  amount  of  steam,  it  would  have 
been  an  easy  matter  to  have  told  him  what  the 
loss  was  in  this  card,  which  cannot  now  be  told. 
It  is  only  an  illustration  of  how  badly  an  engine 
will  work  when  it  is  not  properly  taken  care  of. 

Fig.  42  is  a  diagram  from  the  same  correspon- 
dent, from  a  full  stroke  engine,  doing  from  12  to  18 
horse-power,  and  using  coal  enough  to  run  forty 
horse-power  with  any  kind  of  decent  usage.  The 
cylinder  was  18  inches  in  diameter,  stroke  12 
inches,  100  revolutions  per  minute,  boiler  pressure 
60  pounds,  scale  40,  vertical  engine.  While  this 
is  an  old-fashioned  engine,  and  we  may  expect 
old-fashioned  practice,  it  has  some  peculiarities  of 
its  own  not  at  all  in  its  favor.  A  represents  the 
line  of  boiler  pressure ;  B,  the  admission  line ;  C, 
the  steam  line ;  D,  the  line  of  curiosity ;  E,  getting 
ready  to  exhaust ;  F,  the  exhaust  valve  opens ;  G, 
the  atmospheric  line  of  the  instrument.  The  line 
of  curiosity,  as  we  have  expressed  it,  is  really 
the  pressure  in  the  cylinder  increased  after  the 
expansion  has  taken  place.  This  very  seldom 
occurs  in  well  constructed  engines.  When,  in  all 
probability,  all  the  steam  had  been  given  which 
was  required,  —  the  engine  was  a  double  port 
one,  —  and  after  the  valve  had  made  its  travel,  the 
ports  were  temporarily  opened  during  the  last  of 
the  stroke  of  the  piston ;  therefore  the  piston  of  the 
Indicator  was  raised  by  the  admission  of  more 
steam,  or  the  governor  opened  the  valve  from  a 
changed  speed.  Not  knowing  the  real  construction  of  the  engine,  this  is  only  a 
guess,  but  it  is  one  of  the  things  sometimes  found  in  actual  practice.  In  any 
event,  the  exhaust  of  this  engine  is  about  as  poor  as  it  can  be.  The  valve 
opens  very  slightly  at  E,  commences  to  open  thoroughly  between  E  and  F, 
and  gets  open  so  as  to  reduce  the  pressure  in  the  cylinder  just  before  it  closes 
for  the  admission  line,  B.  We  do  not  wonder  that  our  correspondent  felt 


FIG.  41. 


TWENTY   YEARS    WITH  THE  INDICATOR.  71 

curious,  for  he  has  really  struck  the  old  curiosity  shop  in  Indicator  diagrams ; 
but,  stranger  than  his  personal  adventure,  is  the  fact  that  men  are  still  found 
who  do  and  will  use  engines  making  just  these  same  botch- work  diagrams. 
There  can  hardly  be  two  instances  where  steam  is  worse  misused  than  in  the 


FIG.  42. 


two  diagrams  shown.  Fig.  41  is  entirely  the  fault  of  the  operator;  Fig, 
42  is  really  without  any  remedy,  except  to  put  the  engine  into  the  old  scrap 
pile,  where  it  ought  to  have  been  put  years  ago,  if  fuel  is  of  any  account. 


LESSON   XVIII 


IN  this  lesson  we  have  some  peculiar  looking  diagrams,  and  they  are  also 
peculiar  in  another  sense  —  peculiarly  wasteful.  They  seem  to  be  lacking  in 
every  respect  where  economy  has  any  claim,  and  yet  the  engines  from  which 
these  diagrams  were  taken  are  in  use,  and  undoubtedly  the  men  who  are  using 
them  consider  that  they  have  a  pretty  good  arrangement  for  a  steam  engine. 
The  diagram  (Fig.  43)  really  required  considerable  study  on  our  part  to  ascer- 
tain which  end  up  it  was ;  and  we  only  found,  after  corresponding,  that  the 
party  who  sent  it  to  us  was  not  joking;  he  only  sent  it  as  a  curiosity,  —  some- 
thing which  he  picked  up  in  actual  practice,  no  longer  ago  than  June,  1881. 
The  data,  which  comes  with  it,  is  as  follows :  Diameter  of  cylinder,  1 2  inches ; 
length  of  stroke,  24  inches ;  revolutions  per  minute,  85 ;  boiler  pressure,  75 
pounds;  scale,  20.  As  this  has  a  throttle  regulator,  there  is,  of  course,  no 
approximation  to  the  boiler  pressure ;  the  actual  realized  pressure  on  impact 
is  from  35  to  36  pounds.  The  engine  would  seem  to  take  its  steam  early 
enough,  but  its  carrying  line,  or  steam  line  proper,  has  a  variety  of  contortions 


72  TWENTY   YEARS    WITH  THE  INDICATOR. 

in  it  which  have  no  significance,  no  economy,  do  not  approximate  to  good 
practice,  and  are  all  as  nearly  bad  as  need  be.  The  commencement  of  the 
exhaust,  at  C,  is  the  commencement  of  a  struggle.  The  engine,  as  we  have 
mentioned  before,  takes  steam  at  about  35  pounds ;  when  the  exhaust  valve 
commences  to  open  at  C,  the  engine  commences  to  exhaust  under  precisely 
30  pounds  back  pressure.  After  one-half  of  the  cylinder  has  been  exhausted, 
we  still  find  14  pounds  of  back  pressure  on  the  line,  D,  and  at  the  termination 
of  the  back  pressure,  or  when  the  valve  closes,. we  still  find  8*4  pounds  at  E, 
the  area  of  the  figure,  by  the  Indicator,  showing  that  the  power  exerted  is  295, 
while  the  area  of  the  figure  between  the  diagram  proper  and  the  line  of  rest 
of  the  instrument,  or  the  real  atmospheric  line,  has  an  area  of  229.  In  other 
words,  if  this  engine  were  doing  295  horse-power  by  the  steam  which  is  used, 
it  would  be  working  under  a  back  pressure  of  229  horse-power ;  and  if  the 
back  pressure  were  only  a  little  larger,  it  might  be  a  question  whether  the 


FIG.  43. 

engine  would  run  at  all,  or  if  it  would  not  start  and  run  the  other  way.  We 
believe  that  there  are  not  many  such  engines  as  this  in  use  —  at  least,  we 
should  hope  not.  But  it  is  only  a  question.  No  doubt  the  man  who  con- 
structed this  engine  had  in  his  mind  a  good  working  one,  and  that  he  made 
the  ports  and  the  travel  of  the  valves,  and  the  lap  and  the  lead,  and  all  those 
things,  just  as  nearly  right  as  he  could.  Probably  the  introduction  of  the 
Indicator  would  somewhat,  at  first,  surprise  the  man  running  the  engine ;  but 
if  he  could  not  read  the  lines  to  see  what  was  doing  inside  the  cylinder,  he 
could  evidently  understand,  if  fuel  was  of  any  value  at  all,  after  having  these 
lines  explained  to  him,  that  one-half  the  fuel  which  he  burned  was  a  little 
worse  than  thrown  away,  —  in  fact,  he  was  burning  two  pounds  and  twenty- 
nine  hundredths  to  put  a  brake  on  to  the  two  and  ninety-five  hundredths 
which  did  the  work,  —  whereas,  had  this  engine  been  making  use  of  its  steam 
at  the  same  pressure,  so  that  the  valves  would  have  exhausted  properly,  instead 


TWJ^NTY   YEARS    WITH   THE  INDICATOR.  73 

of  having  295  horse-power  of  work,  and  229  horse-power  of  back  pressure, 
the  outline  of  a  figure,  constructed  to  properly  take  charge  of  the  steam,  would 
yield  426  horse-power ;  hence,  here  is  a  waste  almost  equal  to  one-half  of  the 
fuel,  and,  at  the  same  time,  only  a  trifle  more  than  one-half  of  the  proper  load 
which  the  engine  should  do,  is  being  yielded.  Twice  two  being  four,  the 
engine  is  using  four  times  the  amount  of  fuel  it  should  do  to  develop  the  load 
which  the  Indicator  shows  is  being  done.  Aside  from  the  fact  that  some  men 
still  exist  who  do  not  think  the  Indicator  has  fulfilled  its  mission,  or  that  a  man 
can  set  the  valves  of  his  engine  by  his  eye  or  ear,  jack-knife  or  rule,  this  dia- 
gram would  not  be  worth  the  space  it  occupies. 

In  Fig.  44,  we  have  another  style  of  engine,  a  different  style  of  diagram, 
a  radically  different  result,  —  but  the  same  principles  are  embodied,  —  and 
although  not  to  quite  so  great  an  extent  in  percentage,  the  result  of  loss  is 
much  larger  than  in  the  small  engine.  This  diagram  was  taken  in  a  saw-mill, 


FIG.  44. 

in  the  northern  part  of  Michigan.  We  have  frequently  read  that  a  saw -mill 
was  a  rough  place,  but  we  did  not  suppose  they  would  work  steam  on  exactly 
this  kind  of  a  scale.  The  data,  which  comes  with  this  diagram,  is  as  follows : 
Cylinder,  28  X  28  inches ;  100  revolutions  per  minute ;  boiler  pressure,  105 
pounds;  scale,  40;  the  ports,  2  inches  by  18,  for  steam  ;  exhaust  ports,  3^  by 
[8  inches  ;  lap  on  each  end  of  the  valve,  |f.  This  is  rather  a  peculiar  shaped 
diagram.  The  dotted  line,  A,  is  the  initial  pressure,  80  pounds  ;  the  regulator, 
therefore,  stifles  the  engine  from  25  pounds  of  working  pressure.  The  steam 
ports  of  this  engine  seem  to  be,  for  their  size  and  stroke,  nearer  the  correct 
area  than  the  exhaust  ports,  —  the  difference  in  pressure  in  the  length  of  the 
stroke,  at  the  point  B,  is  only  12  pounds,  —  the  engine,  therefore,  loses  but  12 
pounds  in  carrying  steam  seven-eighths  of  the  stroke  from  the  initial 
pressure,  —  the  initial  pressure  being  80,  and  the  pressure,  at  the  moment  the 
steam  valve  closes,  68  pounds.  This  engine,  in  common  with  many  others  of 


74  TWENTY  YEARS    WITH  THE  INDICATOR. 

the  slide  valve  type,  is  late  in  the  motions  of  its  exhaust.  The  exhaust  valve 
opens,  or  commences  to  open,  rather,  just  above  the  letter  C,  and  here  we  have 
35  pounds  back  pressure  as  the  piston  starts  on  its  return  stroke.  The  exhaust 
is  never  allowed  to  touch  the  atmospheric  line  of  the  instrument,  E.  At  D, 
the  back  pressure  will  be  seen  to  have  increased,  the  smallest  amount  of  back 
pressure  being  three  pounds,  about  what  we  might  expect  in  a  well  regulated 
engine  of  the  family  from  which  this  one  came.  At  D,  the  pressure  increased 
to  nearly  nine  pounds,  and  the  exhaust  valve  seems  to  have  closed.  At  a 
point  above  D,  not  very  well  denned,  the  steam  valve  seems  to  have  opened, 
but  the  pressure  is  not  sufficient  to  carry  the  piston  of  the  Indicator  up  so  but 
that  the  line  leans  away  from  the  vertical  line,  showing  that  the  steam  line 
opens  a  trifle  late.  This  is  a  general  analysis  of  this  diagram. 

The  planimeter  says  that  the  area  of  Fig.  44,  as  described  by  the  Indi- 
cator, is  600 ;  it  also  says  that  the  area  of  the  figure  which  bounds  the  back 
pressure  is  125.  Here  we  have  600  units  of  work  and  125  units  of  worthless- 
ness  in  back  pressure,  or  about  six  times  that  which  should  be  allowed  in  an 
engine  of  this  type  when  in  good  condition.  This  engine  probably  never  did 
exhaust  correctly,  and  without  some  change,  which  cannot  be  determined 
without  further  data,  it  never  will.  If  the  exhaust  port  of  this  engine  is  3^ 
X  1 8  inches,  the  party  who  made  the  examination  should  have  ascertained 
whether  the  same  area  as  the  2X18  was  not  in  some  way  mixed  up  with  thus 
3fij  X  1 8.  He  also  asks  the  question,  What  would  be  the  effect  of  attaching 
a  condenser  to  this  engine  ? 

Briefly,  if  the  exhaust  valves  of  this  engine  will  not  open  better  than  they  do 
now,  the  condenser  will  not  have  a  chance  to  make  much,  if  any,  of  a  vacuum. 
If,  by  changing  your  exhaust  arrangements,  you  can  make  the  exhaust  valve 
open  at  B,  on  the  upper  line,  without  making  it  close  enough  quicker  at  D  to 
lose  by  enormous  compression  what  you  would  gain  by  early  release,  then  your 
condenser  may  possibly  effect  a  great  deal  of  help  to  the  engine.  If  a  saw-mill 
can  afford  to  run  an  engine  under  these  circumstances,  by  burning  sawdust, 
slabs,  or  that  sort  of  trash,  they  may  be  able  to  make  lumber ;  but  an  engine 
of  that  kind,  working  at  that  rate  of  expense  for  fuel,  anywhere  in  this  country 
where  coal  had  to  be  used,  would  ruin  any  concern  with  a  hundred  thousand 
dollars  capital,  in  less  than  five  years,  if  all  the  rest  of  the  branches  of  their 
business  were  well  managed. 

These  diagrams  are  two  of  the  worst  instances  of  the  use  of  steam  that 
have  ever  come  to  the  eyes  of  the  writer.  They  are  neither  uncommon  in 
their  outline,  nor  in  the  fact  that  such  diagrams  can  be  produced,  almost  any 
day,  without  going  ten  miles  from  Boston.  Men  are  running  engines  which 
should  have  been  in  the  scrap  pile  years  ago,  but  the  fact  of  it  is  they  have 
some  cut-off  arrangement,  some  safety -stop  arrangement,  possibly  their  son 
has  invented  something  which  has  been  attached  to  it,  or  they  bought  it  sec- 
ond-hand, and  bought  it  cheap.  It  would  pay  the  users  of  either  one  of  these 


TWENTY  YEARS    WITH  THE  INDICATOR.  75 

engines  to  buy  a  strictly  first-class  engine  of  double  the  capacity  of  either  one 
of  these,  run  in  debt  for  it,  pay  ten  per  cent,  a  year  interest,  and  in  five  years 
they  would  have  the  engine  paid  for,  and  more  than  have  saved  its  cost  in  fuel 
and  in  production.  An  engine  that  is  overloaded  in  this  condition  can  never 
do  its  work  right  or  regularly,  and  any  little  laying  on  of  the  last  straw  will 
break  the  camel's  back  entirely,  —  that  is,  reduce  the  speed  so  that  it  does  not 
work  up  as  it  should.  It  is  a  little  curious  that  so  many  men  pay  no  attention 
to  this  very  important  element  in  our  manufacturing  establishments.  A  very 
little  difference  in  a  mill  of  a  thousand  looms  makes  a  good  profit  on  a  mill 
of  three  or  five  hundred  looms ;  if  the  looms  all  lose  a  pick  a  minute,  in  a 
thousand  loom  mill,  on  64  X  64  goods,  it  makes  nine  pieces  a  day,  or  2,700 
pieces  per  year ;  and  the  fact  of  the  matter  is,  we  have  seen  mills  of  this  size 
which  varied  from  5/^2  to  7  strokes  on  the  engine  in  a  minute,  and  so  on  all 
through  the  day,  making  a  difference  of  several  thousand  pieces  of  cloth  in  a 
year. 


LESSON  XIX 


WE  received  an  invitation  from  an  engineer  friend  to  visit,  with  him,  a 
large  manufacturing  establishment,  in  which  he  would  show  us  something  good. 
The  time  was  set,  and  we  gave  him  an  hour's  leeway  to  get  ready  this  exhibi- 
tion, before  appearing  on  the  scene.  After  waiting  for  some  fifteen  or  twenty 
minutes,  while  his  Indicators  were  attached,  he  showed  us  something  good ;  it 
was  something  wonderful,  at  least  —  not  very  good,  —  and  we  rather  imagine 
he  was  slightly  non-plused  himself  when  he  came  to  show  us  the  original  of 
which  Fig.  45  is  as  near  an  exact  reproduction  as  we  can  make  it.  The  data, 
which  goes  with  this,  is  as  follows:  Corliss  engine,  30^  inches  diameter,  36 
inches  stroke,  revolutions  from  88  to  90,  32  spring ;  boiler  pressure,  at  the 
time  this  particular  diagram  was  taken,  70  pounds ;  duty,  rolling  wire ;  high 
pressure.  A  condenser  was  attached,  but  was  not  working  at  the  time  this  was 
taken. 

Here  are  two  very  peculiar  outlines,  and  all  the  more  peculiar  because  of 
the  complaints  which  our  friend  had  received  that  the  engine  worked  hard. 
We  should  rather  think  it  did  work  hard.  H  and  C  are  respectively  head  and 
crank  ends.  The  engine  is  a  trunk  lighthouse,  cylinder  at  the  top,  crank  at  the 


76  TWENTY   YEARS    WITH  THE  INDICATOR, 

bottom,  driving  a  large  fly-wheel,  from  which  a  3O-inch  belt  conveyed  the 
power.  The  lines,  E,  are  at  right  angles  with  the  atmospheric  line  of  the 
instrument,  and  were  the  basis  of  the  adjustments  which  followed.  These  are 
drawn,  in  order  to  show  whether  the  engine  is  early  or  late  in  taking  steam. 
The  same  letter  refers  to  the  same  lines  upon  all  the  diagrams.  After  the 
diagrams  in  Fig.  45  had  been  taken,  the  question  then  became  of  consequence 
what  to  do  with  the  engine.  It  will  be  seen  that  the  admission  line  upon  the 
head  end  is  late,  —  in  fact,  very  late  indeed ;  so  late  that,  out  of  70  pounds 
boiler  pressure,  only  28  pounds  are  admitted.  While  on  the  crank  end,  the 
Indicator  has  attempted  to  draw  a  map,  and  after  progressing  for  about  three 
or  four  inches  of  the  stroke,  28  pounds  boiler  pressure  are  utilized.  The 
crank  end  is  doing  nearly,  if  not  quite,  double  that  which  the  head  or  upper 
end  is.  There  is  an  approximate  cushion  upon  diagrams  at  B,  but  it  amounts 
to  nothing  practically. 


FIG.  45. 

In  order  to  get  through  with  the  thing  at  the  earliest  moment,  we  sug- 
gested some  changes,  which  were  promptly  made  by  the  gentleman  in  charge, 
while  our  friend  took  the  diagrams.  After  making  two  or  three  changes,  the 
figures  shown  at  B  were  the  result.  In  this  case,  however,  it  will  be  seen  that, 
while  more  steam  enters  the  cylinder,  the  motion  of  the  valves  was  still  very 
far  behind.  Having  adjusted  the  cut-off  so  that  the  two  ends  were  approxi- 
mately correct,  or  balanced  one  with  the  other,  and,  having  used  all  the  leeway 
upon  the  rod  stems,  or  connections,  which  we  dared  to,  the  load  remaining  the 
same  all  the  way  through,  we  then  had  recourse  to  the  eccentric,  sliding  it  over 
on  the  shaft  an  inch  or  more.  From  this  we  obtained  diagrhms  C,  Fig.  47, 
which  are  vastly  different  looking  from  those  of  diagrams  A,  Fig.  45.  All  this 
was  done  within  an  hour,  starting  and  stopping  not  less  than  four  or  five  times. 
We  do  not  know  precisely  the  estimation  in  which  the  gentleman  in  charge  of 
this  engine  holds  the  Indicator,  but  these  three  plates,  which  form  the  subject 
of  our  lesson,  show  the  difference  between  an  engine  which  does  its  work  very 
hard,  and  the  same  engine  given  a  fair  chance  to  do  its  work  easy.  In  Fig.  45 
we  have  28  pounds  of  the  boiler  pressure  admitted  into  the  cylinder.  In 


TWENTY  YEARS    WITH  THE  INDICATOR.  77 

Fig".  46  we  have  40  pounds  admitted  into  the  cylinder.  In  Fig.  47  we  have  52 
pounds ;  therefore,  by  simply  changing  the  position  of  the  valves,  double  the 
steam  is  admitted  into  Fig.  47  that  was  admitted  in  Fig.  45,  and  we  doubt  if 
tnere  are  many  cleaner  cards  found,  than  those  in  Fig.  47  ;  whether  the  engines 
are  in  cotton  mills  or  rolling  mills  is  not  a  matter  of  any  consequence. 

The  cushion  lines,  B,  in  Fig.  47,  conform  very  nearly  to  our  own  ideas  of 
the  proper  amount  of  cushion  for  an  engine,  simply  enough  to  relieve  the  jar 
or  shock,  and  it  makes  little  difference  what  the  amount  of  load  is,  the  cushion 
does  not  increase  with  the  load  in  the  Corliss  engine,  or  in  any  engine  built 
with  the  Corliss  valve.  This  is  a  point  which  slide-valve  makers  do  not 
exactly  appreciate.  If  there  is  any  use  of  the  Indicator  at  all,  there  is  no 
instance  in  which  its  value  can  be  any  clearer  shown  than  in  this  particular 
case.  Here  is  an  engine  doing  regular  work,  in  which  we  presume  the  load  is 
varied  from  15  to  25  horse-power,  sometimes  between  the  very  stroke  of  the 
piston  up  and  down,  and  that  a  hundred  horse-power  variation  can  be  made  in 
less  than  one-half  of  one  minute  when  it  is  doing  its  regular  work. 


FIG.  46. 

If  there  is  anything  in  the  use  of  steam,  the  diagrams  A,  Fig.  45,  show  an 
extraordinarily  bad  working  of  steam  ;  diagrams  B,  Fig.  46,  show  a  desirable 
improvement,  and  diagrams  C,  Fig.  47,  show  a  great  deal  better  work  than 
either  of  the  others ;  and  yet  this  is  the  very  same  engine,  the  same  valves, 
the  same  load,  the  same  speed,  the  same  steam  boilers,  and  only  an  hour's 
difference  from  the  time  of  taking  the  diagrams,  and  no  expense  beyond 
that  of  simply  changing  the  nuts,  and  running  the  rods  out  or  in,  as  was  nec- 
essary to  bring  about  the  adjustment;  and  yet,  if  this  engine  is  doing  300 
horse-power  per  day,  —  and  it  does  do  more  than  that,  —  using  three  pounds 
of  ruel  per  hour,  actually  costing  $4  per  ton,  the  difference  between  the  actual 
result  in  using  the  valves  as  we  found  them,  in  Fig.  45,  or  using  them  as  we- 
1'eft  them  in  Fig.  47,  would  be  a  trifle  over  $12  per  day.  Yet  there  are  some 
'•nor  in  the  world  who  are  so  wise  that  they  consider  that  the  Indicator  has 


;8  TWENTY  YEARS    WITH  THE  INDICATOR. 

outlived  its  days  of  usefulness,  and  that,  while  it  is  a  very  pretty  toy,  "  it  don't 
amount  to  much  in  practice/' 

As  it  may  interest  some  of  our  readers  to  ascertain  how  these  changes 
were  made,  we  shall  take  Fig.  45  for  our  first  analysis.  If  you  refer  to  the 
letters  B,  in  the  corners  where  the  line  of  compression  should  be,  you  will  find 
that  there  is  hardly  an  outline  of  compression  in  either  one.  The  amount  of 
steam  which  is  compressed  is  very  slight.  Rising  above  where  the  compres- 
sion line  strikes  the  admission  line,  following  upward  on  the  line  E,  you  will 
find  that  the  admission  line  gradually  leaves  the  line  E,  more  and  more,  as  it 
approaches  where  the  steam  should  be  cut  off.  And  the  reason  for  this  is  very 
plain.  The  steam  valves  are  terribly  late.  The  exhaust  valve  on  the  head 
end  opens  earlier  than  it  really  needs  to.  It  does  not  open  as  early  in  Fig.  47 
as  in  Fig.  45,  from  the  fact  that  it  was  set  back  by  the  connection.  Now> 


FIG.  47. 

the  question  is  simply,  What  is  needed  to  be  done?  The  straggling  line 
on  the  crank  end,  which  is  marked  C',  simply  means  that  the  valve  opens 
very  slightly  \  the  piston  moves  along  a  little,  and  the  valve  opens  more,  which 
makes  the  line  D ;  when  the  piston  arrives  at  F,  the  valve  commences  to  open 
still  more,  and  finally  it  gets  wide  open  after  the  piston  has  proceeded  so  far 
in  its  stroke  as  G,  —  all  these  letters  referring  to  diagrams  A,  Fig.  45.  Now, 
it  will  be  seen  that  this  carries  steam  clear  over  to  H'  before  it  is  cut  off;  while 
on  the  other  end  it  is  simply  guess-work  to  tell  where  the  cut  off  comes.  Now 
B,  upon  each  of  the  diagrams  A,  Fig.  45,  requires  to  close  the  exhaust  valve 
earlier ;  D,  F,  G  requires  to  open  the  crank  valve  very  much  sooner ;  while  H  , 
as  compared  with  H",  is  much  longer  than  H".  Then  we  must  open  the  crank 
valve  much  sooner  than  before ;  we  must  lengthen  the  cut-off  dog  so  that  the 
crank  end  will  cut  off  much  shorter,  and  we  must  shorten  the  head  cut-off  dog 
so  that  it  will  not  cut  off  so  soon.  Now,  the  exact  quantity  of  movement  to 


TWENTY  YEARS    WITH  THE  INDICATOR.  79 

be  given  any  one  of  these  several  alterations  is  a  matter  of  judgment,  —  no 
man  can  say  a  sixteenth  of  an  inch,  an  eighth  of  an  inch,  two  turns,  or  three 
times  round,  —  but  we  must  always  proceed  with  caution.  Diagrams  B,  Fig. 
46,  show  what  resulted  from  it.  It  will  be  seen  in  C,  that  the  compression  at 
B  has  increased ;  that  instead  of  D,  F,  G,  H,  in  diagrams  A,  Fig.  45,  we  have 
a  very  fair  admission  line  at  D,  and  D',  but  that  both  these  motions  are  still 
late,  as  compared  with  the  line  E.  The  cut  off  is  much  nearer  balanced, 
although  the  head  end  does  not  get  quite  as  much  steam  as  the  crank  end,  C. 
We  have  now  approached  the  limit  of  safety  in  running  the  connecting  rods 
out  of  the  nuts  and  connections,  and  it  does  not  do  to  go  too  far  in  this  direc- 
tion. If  now  we  compare  the  diagrams  B,  Fig.  46,  with  those  of  diagrams  A, 
Fig.  45,  we  notice,  in  general,  that  the  motions  are  much  nearer  uniform  — 
that  is,  both  ends  —  than  they  were  before.  Now,  there  is  only  one  question 
remaining:  Having  "balanced  up,"  as  we  term  it,  the  various  motions,  take 
the  eccentric  and  roll  it  forward  on  the  shaft,  say  an  inch,  for  a  guess.  This  is 
a  quantity  which  can  only  be  measured  by  the  lines  drawn  upon  the  Indicator. 
Fig.  47  shows  what  the  result  of  this  movement  was.  In  this  case,  it  will  be 
seen  that  we  have  very  nearly  "balanced  up,"  although  the  head  end  cuts  off  a 
little  sharper  than  the  crank  end.  The  expansion  lines  are  approximately  well 
disposed  to  each  other,  while  the  compression  at  B  is  just  about  right  for  a  200 
horse-power  engine.  Now,  there  seems  to  be  a  question  as  to  the  right  amount 
of  compression,  or  cushion,  as  it  is  termed.  We  have  therefore  drawn  in  a 
dotted  line  to  show  the  square-cornered  diagram,  which  so  many  people 
admire.  The  only  difference  between  the  line,  B,  which  is  the  actual  line  of 
the  instrument,  and  the  dotted  line,  is,  that  in  the  line,  B,  the  exhaust  valve  is 
completely  closed  at  D,  and  the  piston  of  the  Indicator  gradually  rises  to 
about  the  point  E',  thus  making  24  pounds  pressure.  This  pressure  does  not 
cost  anything,  —  it  simply  confines  so  much  steam,  which  would  otherwise 
be  exhausted, — but  it  does  accomplish  a  very  useful  effect  in  allowing 
the  piston-head  to  cushion  upon  24  pounds  pressure,  and  gradually  bring 
itself  to  rest,  while,  if  the  dotted  line  was  followed,  the  exhaust  valve  would 
not  close  until  D'.  In  this  case,  there  is  nothing  left  for  the  piston  to  cushion 
against,  and  the  whole  arrangement  would  go  a  half  inch  further  if  the 
connection  would  let  it ;  consequently  there  is  that  peculiar  chuckling  noise, 
which  is  frequently  called  pounding,  —  and,  in  reality,  it  is  a  species  of 
pounding,  —  and  sometimes  it  pounds  the  keys  off  in  the  cross-head,  and  the 
cylinder  head  comes  off.  In  other  words,  the  line,  B,  by  closing  the  valve  at 
D,  produces  a  compression,  and  it  eases  the  piston  and  all  the  connections 
back  to  the  crank  in  coming  to  the  dead  center,  or  line  of  rest.  Then,  if  the 
steam  valve  opens  properly,  these  two  lines,  compression  and  admission,  merge 
into  one  another,  so  that  only  an  experienced  man  can  tell  precisely  where  the 
blending  occurs ;  and  just  so  much  steam  as  is  used  by  this  proper  compres- 
sion is  anabsolute  savingof  money  to  whoever  pays  the  bill.  If  fuel  is  of  any 


8o  TWENTY  YEARS    WITH  THE  INDICATOR. 

value,  the  parties  who  are  running  this  engine  will  have  made  a  simple  saving 
of  more  than  $2,000  a  year,  in  difference  between  Fig.  45  and  Fig.  47,  if  they 
will  only  take  as  good  care  of  their  engine  as  the  diagram  C,  Fig.  47,  will 
produce  by  the  fuel. 

These  diagrams  are  not  perfect,  for  the  engine  has  been  in  use  for  a 
number  of  years,  and  they  are  only  given  for  the  purpose  of  imparting  infor- 
mation from  actual  practice. 


LESSON   XX. 


WE  frequently  receive  requests  to  show  the  exact  difference  between  a 
perfect  or  theoretical  use  of  steam  and  the  actual  or  accomplished  use  in 
diagrams.  There  are  so  many  ways  of  constructing  a  hyperbolic  curve,  that 
it  is  well  not  to  confuse  those  readers  who  are  so  much  interested  in  learning 
it,  and,  at  the  same  time,  the  process  and  the  tools  or  instruments  required, 
must  be  confined  to  something  that  does  not  entail  expense  upon  them.  For 
this  purpose  we  have  selected  and  engraved  a  method  which  is  very  nearly 
accurate,  —  sufficiently  so  for  all  practical  purposes.  This  method  was  orig- 
inated by  Prof.  John  Pierce,  of  Providence,  R.  I.,  twenty  years  ago. 

G,  A,  equals  the  clearance  in  the  engine,  and  in  this  our  readers  must  not 
make  any  mistake ;  the  clearance  of  the  engine  is  not  in  proportion  by 
measurement  between  the  piston  head  and  the  cylinder  head  —  which  is  given 
in  this  engraving  —  in  any  well  constructed  engine;  and,  in  figuring  the 
clearance  of  the  engine,  the  steam  and  exhaust  ports  must  be  figured  from  the 
bore  of  the  cylinder  back  to  the  face  of  the  valve,  in  cubic  inches.  The 
amount  of  these  two  calculations  must  be  reduced  to  so  many  inches  of  an 
increase  or  extension  of  the  bore  of  the  cylinder ;  for  instance,  if  we  have  a 
26-inch  cylinder,  and  we  find  that  an  aggregate  of  the  steam  and  exhaust 
ports  added  to  the  clearance  between  the  piston  when  at  full  stroke,  and  the 
piston  head,  amounts  to  265  inches,  it  is  equivalent  to  one-half  inch  of  an 
extended  bore  of  the  cylinder ;  so,  if  it  amounts  to  530  inches,  it  is  equivalent 
to  one  inch  added  to  the  bore  of  the  cylinder.  This  is  how  we  obtain  the 
line,  G  A. 


TWENTY   YEARS    WITH  THE  INDICATOR.  81 

A  B  represents  that  portion  of  the  stroke  which  steam  was  carried ;  B 
represents  the  point  of  cut  off  proper ;  A  C  represents  the  whole  length  of 
the  travel  of  the  piston.  Now  the  line,  G  C,  represents  the  length  of  travel . 
and  the  clearance  included;  A  F  equals  the  steam  pressure  realized  in  the 
cylinder  ;AF  —  GH  —  BE  =  CD.  To  the  line,  A  F,  before  we  com- 
mence to  erect  the  perpendiculars,  we  add  14.7  'pounds  for  the  pressure  of  the 
atmosphere,  so  that  we  should  have  said  A  F  represents  the  boiler  pressure 
and  the  atmospheric  pressure  added  thereto ;  so  that  CD,  BE,  A  F,  G  H, 
are  all  one  and  the  same  thing,  —  the  boiler  pressure  and  the  atmospheric 
pressure,  making  the  absolute  pressure.  Now,  develop  B  C  into  any  number 
of  points  that  is  desired,  —  preferably  making  them  repetitions  of  the  distance 
A  B,  —  numbering  them  i,  2,  3,  4,  join  each  of  these  and  the  point  C  with  H, 
the  joining  lines  intersect  B  E  in  the  points  A,  B,  C,  D,  E ;  then  draw  the  lines, 
i,  2,  3,  4  parallel  to  B  E,  and  at  right  angles  to  B  C,  to  intersect  the  former 
series  of  lines,  H  i,  H  2,  H  3,  H  4,  H  C.  Now,  from  the  line,  B  E,  starting 
at  A,  draw  a  line  at  right  angles  to  B  E,  and  strike  the  first  upright  i ;  wherever 


FIG.  48. 

the  line  A  strikes  the  line  i  at  right  angles  to  B  E,  that  is,  where  the  line  of 
the  expansion  curve,  or  hyperbolic  curve,  should  pass  through  that  point. 
We  have  now  the  line,  A  F ;  draw  the  line,  B  G,  from  B  E  to  2 ;  then  the  line, 
C  H,  from  B  E  to  3,  and  the  line,  D  I,  from  B  E  to  4,  and  the  line,  E  K,  from 
B  E  to  C  D.  The  points  then  given,  F,  G,  H,  I,  K,  are  a  properly  constructed 
hyperbolic  curve,  which  is  approximately  correct,  for  the  line  of  expansion  of 
steam,  according  to  Mariotte's  law.  Now,  all  this  can  be  laid  out  with  a  pair 
of  steel  triangles,  taking  one  having  a  six-inch  leg,  and  its  fellow  may  be 
perhaps  a  four-inch  leg  for  the  long  legs. 

This  is  one  method  of  laying  out  the  hyperbolic  curve.  We  shall,  in  a 
future  lesson,  show  how  some  particular  engine  builders  take,  perhaps,  a  little 
liberty  with  mathematics  or  geometry,  or  may  be  with  facts,  in  describing  the 
line  of  cut  off,  to  satisfy  their  ideas  of  working  steam  expansively.  The  method 
we  have  eiven  is  not,  by  any  means,  the  best  for  laying  out  the  curve,  but  it  is 


82  TWENTY  YEARS    WITH  THE  INDICATOR. 

a  simple  one,  it  is  approximately  correct,  and  it  is  one  that  all  our  engineers 
can  understand.  In  our  next  lesson,  we  shall  show  another  way,  which  is 
.  really  simpler  than  this,  but  this  embodies  the  principles  so  well  that  it  will  be 
well  for  those  following  up  these  lessons  to  take  a  few  cards,  where  the  point 
of  cut  off  is  well  defined,  and  experiment  with  them.  Now,  it  frequently  occurs 
that  an  engineer  wishes  to  test  this  and  not  allow  other  people  to  know  that 
he  has  been  doing  it.  In  that  case,  let  him  take  his  Indicator  diagram,  and  a 
piece  of  tracing  paper ;  then  fasten  the  tracing  paper  over  the  diagram  and  do 
all  his  work  with  a  lead  pencil  upon  the  tracing  paper,  having  put  a  small  tack, 
or  a  drawing  tack,  through  each  end,  or  through  two  corners,  so  that  he 
can  compare  the  lines  without  making  the  least  mark  upon  his  Indicator 
diagram.  He  can  then,  after  having  completed  the  demonstration,  draw, 
with  a  steady  hand,  the  expansion  or  actual  line  of  the  engine  in  a  different 
colored  pencil,  or  by  dotted  line,  and  he  will  then  have  the  whole  thing,  so 
that  he  can  hand  over  the  card  to  some  of  his  better  educated  friends,  perhaps, 
and  let  them  try  their  hands  on  the  same  diagram. 


LESSON  XXL 


IN  this  lesson  we  give  another  method  of  laying  out  the  hyperbolic  curve 
and  where  the  point  of  cut  off  is  clearly  defined.  This  method  is  simple  and 
accurate,  and  can  be  done  upon  any  Indicator  diagram  in  a  few  moments' 
time,  with  a  pair  of  dividers,  a  pencil,  and  a  short,  straight  edge.  In 
Fig.  49,  G  H  —  B  E,  and  both  lines  equal  the  pressure  upon  the  piston,  with 
14.7  added  for  the  atmospheric  pressure ;  hence  the  line,  B  E,  equals  the  boiler 
pressure  and  atmospheric  pressure  combined.  G  B  is  the  length  which  the 
steam  is  carried,  B  being  the  point  of  cut  off.  On  the  lower  line,  H  E  —  G  B, 
and  8,  i=HE,  i,2  =  Ei,  etc.  Divide  the  distance  from  E  to  4,  or  from  B 
to  the  end  of  the  diagram,  into  equal  distances,  which  are  the  repetition  of 
the  distances,  G  B,  and  H  E,  and  from  the  point,  B,  draw  a  line  to  figure  2, 
and  the  point  at  which  this  line  intersects  the  ordinate  i  is  the  point  through 
which  the  hyperbolic  curve  will  pass.  From  B,  through  the  ordinate  2,  draw 
a  line  to  the  point  3,  and  so  on,  drawing  the  line  B  2,  B  3,  B  4,  B  5,  or  what- 
ever the  number  of  points  may  be.  The  line  joins  the  base  line,  H  5,  one 
point  further  from  B  than  the  line  through  which  it  passes.  Whatever  the 


TWENTY  YEARS    WITH  THE  INDICATOR.  83 

point  of  cut  off  may  be  upon  any  diagram,  leave  as  many  spaces  and  one 
more  as  the  length  of  the  diagram  covers.  Then  draw  the  lines  from  the 
point  of  cut  off,  B,  through  each  one  of  the  ordinates,  to  the  foot  of  the  next 
ordinate  beyond,  whether  it  be  five  lines  or  nine  lines ;  then,  by  means  of  a 
curve,  or  the  dividers,  draw  the  hyperbolic  curve  through,  and  you  have  one 
of  the  best  arrangements  for  the  delineation  of  the  actual  line  of  expansion 
that  we  know  of.  This  method,  like  the  one  in  the  previous  lesson,  was 
originated  by  Prof.  Pierce,  of  Providence,  R.  I. 

Fig.  50  is  one  of  the  nearest  approximations  to  a  perfect  Indicator  card 
that  we  have  ever  seen.  The  data,  which  comes  with  this,  is  as  follows : 
Rollins  engine,  built  by  G.  A.  Rollins  &  Co.,  of  Nashua,  N.  H. ;  Corliss  type, 
24  inches  diameter,  42  inches  stroke,  speed  75  revolutions  per  minute,  boiler 
pressure  75  pounds,  scale  40;  new  engine,  in  the  Cleveland  Rubber  Com- 
pany's factory,  Cleveland,  Ohio ;  74/^  pounds  of  the  boiler  pressure  realized 
in  the  cylinder.  The  engraving  is  an  exact  fac  simile  of  the  card  which  came 


FIG.  49. 

from  the  Indicator,  and  was  not  a  tracing.  The  steam  line  is  perfectly  elegant, 
and  is  as  straight  as  we  ever  saw.  The  expansion  line  has  a  little  variation, 
which  is  no  doubt  caused  by  the  instrument.  The  exhaust  line  is  as  nearly 
perfect  as  the  steam  line;  the  slight  amount  of  compression  shows  a  very 
finely  working  exhaust  valve,  while  the  admission  line  is  just  as  nearly  right 
as  it  can  be.  This  is  simply  an  elegant  Indicator  card  from  actual  practice^ 
and  leaves  very  little  to  be  desired.  Those  of  our  engineers  who  are  running 
Corliss  engines,  and  are  practicing  with  the  Indicator,  may  imitate  this  card  as 
near  as  they  can,  and  may  rest  assured  that  when  they  reproduce  it  they  are 
doing  as  near  the  best  of  anything  possible  as  they  will  ever  do.  Every 
motion  of  the  valve  is  smooth  and  clear,  and  some  of  our  beginners  will  do 
well  to  take  this  as  a  model  to  apply  the  curve  to,  by  either  of  the  methods 
given  in  this  or  the  previous  lesson,  and  figure  up  the  percentage.  In  this 
engine,  no  excess  of  compression  or  cushioning  is  used,  steam  is  given  at  the 
right  place  and  at  the  right  time,  the  corners  are  perfectly  sharp  and  clear,and 


84  TWENTY    YEARS  WITH  THE  INDICATOR. 

very  well  defined;  and,  when  we  say  it  is  one  of  the  handsomest  specimens  of  a 
card  or  diagram  from  actual  practice,  we  merely  tell  the  whole  story,  and  state 
a  fact.  Messrs.  Rollins  &  Co.  are  to  be  congratulated;  and  we  know  that 
Mr.  Rollins  himself  is  a  close  student  of  the  Indicator,  and  a  man  who  profits 


FIG  50. 

by  his  experience  with  it.  While  we  do  not  know  the  fact  in  this  relation, 
we  have  no  doubt  that  he  has  profited  by  the  practical  application  of  the  Indi- 
cator in  the  perfection  which  he  has  attained  in  the  handling  of  his  steam  and 
exhaust  valves. 


LESSON  XXII. 


THIS  lesson  illustrates  another  instance  of  experimenting.  The  diagrams  in 
question  areour  own,  taken  from  an  engine  having  a  Corliss  cylinder  16  inches 
diameter,  42  inches  length  of  stroke,  intended  to  be  run  at  55  revolutions, 
with  comparatively  little  regulation,  steam  pressure  6c;  rounds,  scale  30. 

The  diagram,  H  R,  Fig.  51,  is  from  the  head  end  of  the  cylinder,  as  we 
found  it  working,  and  presents  some  peculiar  characteristics.  The  admission 
line  is  a  peculiarly  lazy  one,  and  the  serration  at  A,  it  will  be  seen,  is  repeated 
four  times  distinctly  before  the  steam  line,  B,is  really  commenced.  When  the 
steam  line  is  finally  started  at  B,  it  will  be  found  to  be  one-sixth  of  the  whole 
stroke  before  the  steam  valve  becomes  completely  open.  The  steam  line  is 


TWENTY   YEARS    WITH  THE  INDICATOR.  85 

then  maintained  very  well;  but  with  steam  65  pounds  in  the  boiler,  there  is 
only  52  pounds  on  the  piston  This  is  entirely  too  much  of  a  difference.  If 
it  was  two  or  three  pounds,  or  five  pounds  even,  upon  this  size  of  an  engine, 
and  at  this  speed,  it  would  not  be  so  very  considerable.  If  it  were  a  five  or 


FIG.  51-  FIG.  52. 

six  hundrerl  horse-power  engine,  and  the  difference  was  seven  or  eight 
pounds,  we  should  not  think  so  much  about  it  on  account  of  the  volume 
of  steam,  as  in  this  case,  where  the  volume  is  so  small,  and  the  engine  is 
situated  so  near  the  boilers.  It  will  be  noticed  that  the  admission  line 
leans  very  much  too  far  away  from  the  upright  we  have  erected. 


86  TWENTY  YEARS    WITH  THE  INDICATOR. 

Leaving  the  connection  of  the  steam  line  with  the  cut  off  at  C,  we  ha\  e 
the  expansion  line,  C  C  D,  with  some  peculiar  looking  steps  in  it.  Exactly 
what  causes  these  steps  is,  to  a  certain  extent,  conjecture  in  any  ordinary 
engine.  In  this,  there  is  no  conjecture  about  it;  the  engine  is  badly  regulated, 
and  is  jumping  about ;  the  load  is  variable,  and  we  should  not  be  surprised 
even  to  find  saw  teeth  all  the  way  down  the  length  of  the  expansion  curve. 
In  fact,  the  serrations  are  visible  far  below  the  second  C.  This  is  caused  by 
the  very  unequal  action  of  the  regulator  in  giving  different  impulse  to  the 
piston,  and  by  the  peculiar  action  of  the  ever-varying  load. 

At  D  we  commence  to  exhaust.  Curiously,  the  piston  of  the  Indicator  is 
held  up  for  one-twelfth  of  the  stroke,  and  a  pressure,  at  D  E,  of  12  pounds,  is 
exerted  against  the  piston.  Ordinarily  we  might  ask,  Why  was  this  peculiar 
point?  In  this  case  it  is  easily  explained.  This  engine  —  the  dimensions 
already  given  —  is  expected  to  exhaust  through  a  five-inch  exhaust  pipe, 
while  it  is  fed  through  a  five-inch  pipe  and  a  six-inch  valve,  as  though  the 
valve  could  increase  the  capacity  of  receiving  steam  from  the  boiler  which  was 
throttled  in  a  five-inch  pipe.  When  the  exhaust  commences  at  D,  there  is 
twelve  pounds  back  pressure  between  D  and  E,  E  representing  the  termination 
of  the  atmospheric  line  of  instrument.  After  the  steam  is  started  to  exhaust, 
all  men,  who  are  conversant  with  it,  know  that  a  current  of  steam  will  soon  aid 
essentially  in  relieving  the  pressure;  hence,  it  requires  one-twelfth  of  the 
stroke  to  establish  this  current  in  the  exhaust  pipe.  It  commences  to  decrease 
the  pressure  at  F,  and  from  there  to  the  end  of  the  stroke,  or  at  G,  the  back 
pressure  is  gradually  reduced,  in  no  case  being  less  than  three  pounds.  There 
is  a  certain  way  out  of  this  in  the  proper  adjusting  of  the  valves.  Its  mate, 
diagram  H  S,  Fig.  56,  was  taken  from  the  same  end  of  the  same  engine,  and 
shows  what  improvement  can  be  made  by  even  a  little  adjustment ;  and,  for 
the  sake  of  relieving  the  exhaust  pipe,  the  load  was  very  materially  reduced  in 
this  diagram,  to  ascertain  whether  the  engine  would  exhaust  freely  with  a 
lighter  load  or  not. 

This  is  a  very  practical  illustration  of  what  may  be  accomplished  in  an 
hour's  time  by  the  proper  application  of  the  Indicator.  It  will  be  seen  that 
the  Indicator  will  not  increase  the  amount  of  steam  drawn  through  a  too  small 
pipe,  nor  will  it  make  less  steam  than  is  actually  present.  The  diagram,  H  S, 
Fig.  52,  shows  how  the  steam  can  be  admitted  properly,  so  far  as  the  capacity 
of  the  valve  motion  and  valves  will  admit.  C  C,  in  the  diagram  H  S, 
shows  us  conclusively  that  there  is  a  little  lost  motion  —  probably  in  the  valve 
in  the  stem. 

Time  was  not  allowed  for  a  full  bringing  up  to  the  standard  of  this  engine, 
as  the  question  was  between  the  builder  and  purchaser  as  to  whether  it  was  in 
good  condition ;  and,  until  further  changes  are  made  in  the  work,  it  is  impos- 
sible to  bring  it  up  to  standard.  The  lesson,  however,  is  instructive  to  those 
who  are  watching  these  points,  and  if  any  of  our  readers  desire  to  apply  the 


TWENTY  YEARS    WITH  THE  INDICATOR.  87 

hyperbolic  curve,  erect  the  upright  in  the  same  scale  precisely  to  the  extent  of 
65  pounds ;  take  the  same  point  of  cut  off,  carry  their  expansion  line  out,  and 
see  what  the  actual  percentage  of  the  work  done  by  this  engine  is,  with  the 
steam  that  should  be  in  the  cylinder  if  the  pipes  had  been  properly  connected, 
and  the  valves  had  done  their  work.  If  any  of  them  try  this,  they  will  be 
astonished,  and  it  will  be  an  interesting  and  instructive  example. 


LESSON   XXIII. 


WE  have  something  in  this  lesson  of  more  than  ordinary  interest,  and 
from  which  we  can  learn  something  in  reference  to  real  economy.  The  card, 
W  C,  Fig.  53,  came  from  a  reliable  party,  and  was  taken  from  an  engine  built 
some  years  since  to  do  350  horse-power.  The  dimensions  and  data  are  as 
follows :  Cylinder  28  inches  diameter,  5  feet  stroke,  50  revolutions,  steam -pipe 


FIG.  53. 


6  inches  diameter,  exhaust-pipe  7  inches  diameter,  steam  ports  24^6  inches 
area,  exhaust  ports  24.5  inches  area,  balanced  poppet  valve  and  automatic  cut- 
off, scale  30;  steam  pressure  50  pounds,  which  is  one  of  the  most  peculiar 
features  of  the  whole  diagram.  The  line,  E,  in  the  diagram,  W  C,  Fig.  53,  is 


88  TWENTY   YEARS    WITH  THE  INDICATOR. 

the  line  of  rest  of  the  instrument,  or  the  atmospheric  line  of  rest ;  the  dotted 
line,  A,  is  the  line  of  steam  pressure.  We  have  assumed,  in  our  calculation, 
that  the  engine  should  have  carried  steam  on  the  dotted  line,  A,  instead  of 
which,  when  it  cuts  off  at  B,  it  has  fallen  15  pounds  from  boiler  pressure.  The 
dotted  line  shows  the  expansion  curve  had  the  engine  cut  off  at  boiler  pressure. 
It  will  be  seen  that  the  steam  line  is  quick  rather  than  late  in  its  movement, 
and  that,  when  the  valve  is  open,  the  steam  pressure  is  maintained  for  so  brief 
a  period  of  time  that  it  makes  simply  a  point.  The  steam,  therefore,  com- 
mences instantly  to  fall  away  from  the  boiler  pressure,  and,  as  the  piston 
commences  to  travel  away,  its  motion  is  slightly  increased,  and  the  boiler 
pressure  falls  correspondingly.  On  being  cut  off,  at  B,  the  real  line  of  the 
engine  is  found  at  C,  and  without  going  into  the  niceties,  its  approximation  to 
the  real  theoretical  curve  below  would  lead  us  to  infer,  and  with  very  good 
reason,  that  the  valves,  after  closing,  were  not  tight,  or  that  some  re-evapora- 
tion took  place.  When  the  exhaust  valve  does  open,  and  the  vacuum  line,  D, 
is  made,  the  condenser,  when  it  gets  hold,  only  gives  us  two  pounds,  or  four 
inches ;  after  traveling  one  foot  we  have  four  pounds,  in  the  middle  of  the 
stroke  we  have  five  pounds,  and  at  the  heel  of  the  exhaust  we  have  six  pounds, 
or  twelve  inches,  as  the  largest  amount  of  vacuum  obtained.  The  line,  F,  is 
the  line  of  absolute  vacuum,  or  14.7  pounds ;  it  will  be  seen  that  we  do  not,  in 
the  largest  measure  accomplished,  quite  reach  one-half  of  the  vacuum,  which 
we  should  have  done.  There  are  two  points  about  this  diagram  which  abso- 
lutely corroborate  what  we  shall  find  if  we  turn  to  the  area  of  the  steam  ports 
and  exhaust  ports,  and  that  is,  that  they  are  both  insufficient  to  do  the  amount 
required  with  that  size  cylinder  and  that  size  engine.  The  steam  ports  are 
shown,  conclusively,  to  be  very  lame  in  their  dimensions,  by  the  instantaneous 
falling  off  of  the  boiler  pressure,  the  moment  the  valve  is  opened  and  the 
cylinder  begins  to  travel ;  cutting  off,  at  about  one-quarter  the  stroke,  we  lose 
15  pounds  boiler  pressure,  and  when  the  exhaust  valve  opens,  for  the  con- 
denser to  operate,  we  get  2,  4,  6  pounds  vacuum,  instead  of  8,  10,  12.  These 
two  things  show  conclusively,  therefore,  that  this  engine  never  was  fit  to  run 
with  economy  at  that  speed ;  it  might  have  done  very  well  at  one-half  the 
speed,  or  perhaps  30  to  35  revolutions.  The  party  who  sent  it  wrote  as 
follows :  "  The  engine  was  unable  to  perform  the  350  horse -power  with  any 
sort  of  economy,  and  came  near  ruining  the  parties  by  reason  of  their  very 
large  coal  bills  and  irregular  speed." 

In  another  engine  of  the  same  general  type,  we  have  the  diagrams  C  C, 
Fig.  54,  from  a  Wright  engine,  thirteen  years  in  use,  with  22  inch  cylinder,  42 
inch  stroke,  63^  revolutions,  scale  of  40  pounds,  boiler  pressure  78  pounds, 
non-condensing.  The  diagram,  which  we  reproduce,  is  one  of  a  pair  upon  the 
same  card,  and  shows  52^  pounds  of  steam  at  the  moment  of  impact,  or  at 
A.  The  dotted  line,  B,  represents  the  realized  pressure.  This  engine  carries 
its  pressure  to  the  point  of  cut  off  with  a  loss  of  only  three  pounds.  The 


TWENTY   YEARS    WITH  THE  INDICATOR. 


89 


expansion  line  is  very  good ;  the  exhaust  valve  opens  and  closes  well,  and  the 
difference  between  the  exhaust  line  and  the  atmospheric  line,  of  2^  pounds,  is 
partially  caused  by  using  steam  for  heating.  If  we  were  running  this  engine, 
we  should  open  the  exhaust  valve  quicker,  so  as  to  avoid  the  initial  back 
pressure  on  the  dotted  line,  C,  and  to  try  and  open  it  more  in  the  line  of  D. 
This  would  probably  give  us  a  little  more  compression,  which  would  be  all  the 
more  favorable,  as  shown  at  E,  and  would  relieve  the  engine,  so  far  as  it  can 
be  relieved  from  its  peculiarities  of  make.  Evidently,  this  engine  has  been  in 
the  hands  of  parties  who  have  taken  good  care  of  it,  else  it  would  never  have 
made  thirteen  years'  time,  showing  such  good  lines  as  it  does.  The  most 
serious  fault  about  it  is,  its  lack  of  realizing  the  boiler  pressure ;  whether  it  is 


FIG.  54. 


caused  by  pipes  we  cannot  say,  not  having  that  data  given,  and  there  is  not  in 
this  diagram  anything  to  show  that  the  steam  passages  and  exhaust  passages 
are  stifled,  as  in  its  fellow,  Fig.  53. 

The  difference  between  these  two  engines  is,  simply  and  purely,  that  C  C^ 
Fig.  54,  will  do  much  more  work  with  the  same  fuel  than  W  C,  Fig.  53. 
Whether  C  C,  Fig.  54,  could  be  improved  by  increasing  the  size  of  the  steam 
pipe  and  exhaust  pipe,  we  do  not  know.  These  diagrams  are  from  actual 
practice,  and  are  all  the  more  interesting  because  they  are  so ;  both  are  from 
the  same  type  of  engine  generally,  although  some  differences  exist,  and  the 
point  is  conclusively  shown  that,  if  one  is  faulty,  there  is  no  reason  that  the 
other  need  be,  or  for  any  real  cause  on  account  of  the  system  adopted. 


TWENTY  YEARS   WITH  THE  INDICATOR. 


LESSON   XXIV. 


IN  this  lesson  we  have  diagrams  taken  from  condensing  engines  from  two 
different  builders.  The  differences  in  practice,  in  the  condensing  engines,  are 
quite  as  radical  as  in  the  high  pressure  or  non -condensing  engines,  both  as  to 
valve  gear  movements,  and  control  of  the  valves,  regulation,  and  the  vacuum ; 
and,  as  the  vacuum  is  the  important  part  of  the  condensing  engine,  we  have 
chosen  engines  which  are  not  fitted  with  any  of  the  patent  condensers,  or  the 
portable  or  attachable  condensers,  whatever  they  may  be  called,  both  having 
the  air-pump  condenser,  or,  as  it  is  generally  termed,  the  old-fashioned 
condenser. 


FIG.  55. 

A  M,  Fig.  55,  is  a  Corliss  engine,  which  has  been  running  nearly  thirty 
years,  and  was  one  of  the  first  ones  built  where  it  was  to  be  run  for  economy 
over  some  other  one.  The  diagram  is  from  a  32 -inch  cylinder,  7  feet  stroke, 
running  36  revolutions,  40  pounds  of  steam,  vacuum  gauge  27^,  scale  20. 
Thirty-four  pounds  of  steam  are  put  into  the  cylinder ;  the  steam  line  is  almost 
absolutely  straight  —  does  not  vary  half  a  pound ;  the  expansion  line  is  very 
good;  if  anything,  we  would  open  the  exhaust  valve  sooner,  allowing  the 
condenser  to  get  hold  earlier  in  the  stroke,  and  yet  the  vacuum,  at  one-third 
stroke,  measures  20  inches,  and  further  along  22  inches,  bearing  in  mind  that 


TWENTY  YEARS    WITH  THE  INDICATOR.  91 

this  22  inches  is  in  the  cylinder.  Aside  from  the  alteration  of  the  exhaust 
valve,  hardly  anything  is  desired  in  this  diagram.  If  the  exhaust  valve  should 
open  earlier,  so  as  to  allow  the  condenser  access  to  the  steam  quicker,  the 
value  of  the  vacuum  would,  without  doubt,  be  BH^H^H^^^BHIMHIHHHI 
increased  from  three  to  five  per  cent.,  and 
might  be  more  than  that. 

This  engine  has  been  noted  for  its  econ- 
omy, and  has  produced  very  gratifying  results 
to  its  owners.  The  steam  valves,  which  are 
now  working  in  this  engine,  have  been  in  use 
for  many  years,  without  change,  but  there  is 
just  this  difference:  the  engine  has  been  well 
taken  care  of,  —  although  it  has  been  idle  for 
some  time,  —  and  the  diagram  shows  plainly 
enough  that  one  of  the  objections  that  many 
people  urge  against  the  Corliss  engine  has  no 
real  foundation  in  fact,  when  the  engine  has 
received  the  same  care,  or  really  less  care  than 
some  others,  where  parties  make  such  an  out- 
cry about  semi-rotary  valves.  In  this  place  we 
'must  judge  the  engine  by  what  it  absolutely 
produces,  not  by  any  man's  preferences  or 
prejudices,  and  although  this  is  an  old  machine, 
it  certainly  makes  a  card  that  speaks  well  for 
its  maker  and  for  its  users. 

In  contrast  to  this,  we  present  a  diagram 
from  an  engine  built  by  Hicks  &  Hargrave,  in 
England,  some  years  since,  now  in  operation 
in  a  New  England  cotton  mill.  The  data  is  as 
follows:  Horizontal,  2O-inch  cylinder,  42-inch 
stroke,  62  revolutions  per  minute,  spring  40, 
boiler  pressure  70,  vacuum  28,  hot  well  no. 
This  engine  (diagram  H  H,  Fig.  56)  has  four 
grades  of  cut-off,  which  can  be  varied  by  hand, 
while  the  engine  is  running,  —  double-balanced  FlG>  56> 

poppet  steam  valves,  5^   inches,  and  the  same  style  of  exhaust  valves  6^2 
inches  in  diameter,  with  a  double-balanced  throttle  valve  and  ball  regulator. 

We  have  erected  the  line  at  right  angles  to  F,  which  is  the  atmospheric 
line  of  the  instrument,  to  show  that  the  motions  of  the  valves  are  very  late  in 
opening,  as  the  steam  valve  only  opens  after  the  piston  has  traveled  from 
the  upright  line  to  A.  The  cut  off  takes  place  slightly  before  B  ;  the  expan- 
sion line  is  excellent  from  B  to  C ;  at  C  the  exhaust  valve  opens,  —  and  this  is 
one  of  the  best  forms  of  exhaust  in  any  engine,  either  condensing  or  non-con- 


92  TWENTY  YEARS    WITH  THE  INDICATOR. 

densing,  —  and  exhausts  early  enough  to  allow  a  sharp  falling-off  ol  pressure 
a  little  before  the  piston  finished  its  stroke.  The  vacuum  is  24  inches  almost 
at  the  start,  and  26  inches  at  the  center  of  the  stroke.  The  valve  commences 
to  close  at  B,  and  is  quite  closed  at  E,  while  the  steam  valve  commences  to 
open.  This  diagram,  it  must  be  remembered,  is  by  a  regulator  which  throttles 
the  steam  in  the  main  pipe.  And,  in  contrast  to  the  dimensions  of  pipes  given 
in  our  last  lesson,  this  engine,  with  a  2O-inch  cylinder,  has  a  six-inch  steam 
pipe,  instead  of,  as  in  one  of  the  diagrams  in  the  same  lesson,  having  a  28-inch 
cylinder  and  a  six-inch  pipe.  This,  therefore,  accounts  for  the  loss  between 
boiler  and  realized  pressure  in  the  cylinder,  the  boiler  pressure  being  70,  and 
the  realized  pressure,  between  A  and  B,  only  52  pounds.  This  engine  has 
been  running  economically  for  some  twelve  years,  although,  perhaps,  the 
position  of  the  valves  might  be  improved  somewhat,  so  as  to  increase  their 
economy.  These  are  very  considerably  different  in  design  and  practice,  both 
being  intended,  practically,  to  accomplish  the  same  economical  result.  We 
have  not  the  figures,  nor  is  that  the  purpose  of  the  article,  which  is  only  to 
show  the  actual  difference  in  practice  between  the  makers ;  and  this  may  be 
still  a  very  good  card  for  an  engine  regulating  at  a  fixed  cut  off  by  a  double 
pressure.  The  pressure  is  governed  by  the  regulator. 


LESSON  XXV. 


THE  diagrams  illustrated  in  this  lesson  are  again  the  result  of  actual 
practice  and  a  search  after  information.  The  data  is  as  follows :  Engine  10 
inches  by  24  inches,  72  revolutions,  67  and  68  pounds  boiler  pressure,  40 
spring.  Diagrams  F  F  A,  Fig.  57,  is  the  engine  as  it  was  found ;  the  line  at 
the  left  is  the  boiler  pressure ;  the  distance  from  this  line  to  the  dotted  line,  F, 
is  the  distance  the  piston  traveled  before  the  valve  was  fully  opened.  It  will 
be  seen  that  the  valve  made  a  series  or  succession  of  efforts  to  open,  repre- 
sented by  the  letters  A,  B,  C,  D.  These  will  need  no  explanation  to  the  man 
who  thinks,  —  that  the  first  movement  of  the  piston  is  slow  as  it  moves  away 
from  the  center,  and  that,  as  the  motion  is  accelerated,  each  one  of  these  steps 
moves  farther  away  from  the .  perpendicular  line  representing  the  boiler 
pressure;  and  at  each  one  of  these  steps,  or  stages,  it  will  be  seen  that  the 
pressure  increases  until,  finally,  the  steam  line,  E,  is  reached.  The  cut  off  is 


TWENTY   YEARS    WITH  THE  INDICATOR.  93 

reasonably  sharp,  but  it  is  terribly  late.  The  line,  F,  is  dotted  through  the 
steam  line,  E,  to  show,  that  of  68  pounds  boiler  pressure,  37  pounds  only  are 
realized  upon  the  piston  head,  with  this  very  late  opening ;  while,  if  we  refer 
to  the  other  end  of  the  diagram,  we  shall  find  that  47  pounds  are  realized ; 
and,  if  we  look  at  H,  we  find  the  departure  from  the  perpendicular  line  is 
about  one-fifth  of  what  it  is  at  the  other  end  of  the  engine.  In  other  words, 
the  valves  upon  the  left  card  open  after  the  piston  has  moved  away  three 
inches,  while  upon  the  right  the  valve  commences  to  open  after  the  piston  has 
moved  three-eighths  of  an  inch,  and  is  quite  open  at  one  inch.  The  opening, 
after  the  piston  has  receded  one  inch,  reduces  the  realized  pressure  from  68  to 
47,  whereas,  in  the  other  end  of  the  engine,  we  have  only  37  pounds  of  real- 
ized pressure  out  of  the  68 ;  this  shows,  therefore,  that  the  rule  is  well  founded 
that  when  the  valves  do  not  open  promptly,  the  loss  of  pressure  increases  in 
proportion  as  the  valves  are  late  in  their  movements.  It  will  not  be  necessary 


for  us  to  give  any  rule  for  this,  for  our  readers  must  endeavor  always  to  avoid 
rather  than  to  approximate ;  for  that  reason  we  omit  it.  It  is  a  self-evident 
fact  that  this  engine  is  doing  badly  enr  ugh,  and  yet  it  is  not  the  worst,  by  any 
means,  of  those  which  we  have. 

Turning  to  diagrams  F  F  B,  Fig.  58,  we  have  the  same  engine,  same 
dimensions,  same  speed,  and  approximately  the  same  boiler  pressure,  but  the 
valves  have  been  readjusted  in  their  opening,  and  already  show  a  very  radical 
improvement.  In  this  case,  we  have  sixty-seven  pounds  boiler  pressure, 
instead  of  sixty-eight,  as  in  the  other  set  of  diagrams ;  d  represents  the  boiler 
pressure ;  the  left  hand  diagram  opens  the  valve  a  little  quicker  than  we  should 
advise ;  the  right  hand  diagram  a  trifle  later,  but  very  nearly  right.  At  A  the 
admission  should  come  nearer  the  perpendicular  line.  It  will  be  seen  that  the 
admission  touches  the  perpendicular  line  at  the  top,  or,  as  the  boiler  pressure 
was  nearer  realized  while  on  the  other  card,  at  B,  the  Indicator  line  leans 
slightly  away  from  the  perpendicular  line ;  therefore,  the  motion  at  A  is  a  little 
too  quick,  and  at  B  is  a  little  too  slow,  and  there  is  also  rather  too  much 


94  TWENTY  YEARS    WITH  THE  INDICATOR. 

cushion  at  A.  The  steam  line,  in  this  case,  is  peculiar  to  poppet  valve  engines 
that  run  at  high  speed.  The  left  hand  card  falls  away  from  the  steam  line  ten 
pounds  at  the  cut  off,  c,  and  it  is  very  nearly  or  quite  the  same  upon  the  other 
card  at  the  approximate  cut  off,  or  the  same  point.  In  this  case,  the  boiler 
pressure  is  not  realized  within  five  or  six  pounds ;  at  the  same  time  the  dia- 
grams are  immensely  superior  to  those  of  F  F  A. 

While  we  know  nothing  of  the  result  of  this  change,  as  regards  the  fuel, 
we  are  safe  in  saying  that  diagrams  F  F  A  will  probably  do  one-half  the  power 
of  diagrams  F  F  B ;  and  that  it  would  cost  from  fifty  to  one  hundred  per  cent. 


FIG.  58. 

more  coal  to  do  it,  to  say  nothing  of  the  better  regulation  of  the  engine,  with 
the  diagrams  F  F  B.  This  adjustment  is  something  which  can  be  done  by  any 
good  steam  engineer  who  has  the  Indicators,  and  who  will  give  a  little  time 
and  attention  to  them.  If  our  mill  owners  and  power  users  would  resort  to 
the  Indicator  more,  there  would  be  less  growling  about  incompetence,  and 
much  more  satisfactory  results  in  the  combustion  of  fuel,  more  power  would  be 
realized  from  the  same  coal,  better  work  and  less  repairs,  and  generally  a  very 
much  better  tone  in  and  about  engine  rooms  and  among  power  users. 


LESSON   XXVI. 


IN  this  lesson,  we  shall  illustrate  the  Planimeter,  as  applied  to  the  practical 
measurement  and  computation  of  the  Indicator  diagrams,  giving  plain  direc- 
tions how  to  use  it,  and  what  not  to  do.  The  Planimeter  was  invented  in  1827, 
by  a  Swiss  engineer  named  Oppenkofer.  In  1849,  another  Swiss  engineer, 


TWENTY  YEARS    WITH  THE  INDICATOR.  95 

named  Welty,  made  considerable  improvements  over  Oppenkofer,  but  these 
instruments  were  heavy,  bulky,  and  not  adapted  to  general  use.  In  1854, 
M.  J.  Amsler,  a  mathematical  professor  at  Schaffhausen,  succeeded  in  making 
the  Polar  Planimeter,  and  again  this  has  been  simplified  materially.  Our 
illustration,  Fig.  59,  shows  the  Amsler  Planimeter,  as  manufactured  by  the 
American  Steam  Gauge  Company,  of  Boston.  The  Planimeter  is  a  surface 
measurer,  or,  we  might  say,  a  plane  measurer,  for  measuring  the  area  of  any 
irregular  form  that  may  exist  upon  paper,  to  reduce  it  to  the  exact  area  con- 
tained in  that  form  upon  any  scale  which  may  be  applied  to  it.  In  other 
words,  the  Planimeter  computes  the  area  of  any  form  which  may  be  submitted 
to  it,  when  properly  handled,  doing  it  by  a  mechanical  process  rather  than  a 
mental  one.  As  shown,  it  is  but  little  larger  than  a  pair  of  dividers,  and  is 
enclosed  in  a  nicely  lined  and  leather  covered  case,  which  can  be  readily 
carried  in  the  pocket,  is  always  ready  for  use,  and,  with  a  little  care,  will  last 
for  years.  Substantially  this  has  been  explained  and  the  Planimeter  illustrated 
on  a  previous  page,  but  we  have  also  added  to  this  explanation  the  general 
features  of  the  computation  of  the  Planimeter,  as  applied  to  "working  out" 
the  Indicator  diagram. 

We  have  taken  a  high-pressure,  or  non-condensing  card,  G  M,  Fig.  59, 
and,  for  the  sake  of  computation,  we  shall  put  the  following  data  with  it: 
Diameter  of  cylinder  24  inches,  length  of  stroke  60  inches,  60  revolutions  per 
minute,  30  spring.  When  using  the  Planimeter,  we  take  a  piece  of  thick 
pasteboard,  and  get  the  bookbinder  to  paste  a  sheet  of  good  blotting  paper 
upon  it,  pressing  it  over  night,  or  until  thoroughly  dried.  We  never  use  a 
finished  or  sized  paper,  or  one  that  has  a  polis-h  on  it  like  glass.  The  surface 
of  this  paper  should  be  kept  free  from  bunches,  projections,  grit,  paste,  or 
dirt.  A  piece  of  blotting  paper  can  be  pasted  upon  a  pine  board,  well 
seasoned,  and  the  board  hung  up  out  of  the  way,  when  not  in  use,  in  the 
engine  room  or  office.  A  piece  of  drawing  paper  can  be  pasted  upon  a  board, 
or,  for  immediate  use,  any  piece  of  brown  paper  which  is  even  on  its  surface, 
not  having  bunches  or  projections,  can  be  drawn  out  on  a  smooth  board,  and 
the  Planimeter  set  up  at  once. 

Referring  to  Fig.  59,  the  point,  A,  must  be  outside  of  the  diagram,  or 
outside  of  the  area  to  be  measured.  The  index  roller,  C,  must  travel  smoothly 
over  the  paper,  and  anything  which  interferes  with  its  travel  interferes  with  the 
correctness  of  the  computation  to  be  made.  Grit,  dust,  oil,  or  any  foreign 
matter,  makes  your  computation  at  once  worthless.  The  tracing  point,  B,  is 
what  you  will  take  between  the  thumb  and  fore-finger,  running  it  around  the 
figure  in  the  same  direction  that  the  hands  of  a  watch  travel.  The  point,  A,  is 
the  stationary  one,  and,  having  placed  your  diagram,  you  can  change  the 
point,  A,  into  any  position  you  like  that  will  not  allow  the  roller,  C,  to  come  in 
contact  with  the  edge  of  the  Indicator  diagram,  but  will  reach  the  most  remote 
point  of  the  line  traced  by  the  Indicator,  without  touching  the  paper  on  which 


96  TWENTY   YEARS    WITH   THE  INDICATOR. 

the  diagram  is  traced.  Let  it  roll  freely  upon  the  paper  which  forms  your 
table.  In  starting  with  the  point,  B,  we  usually  do  so  in  the  corner  of  the  card, 
or  any  convenient  point,  taking  care  that  a  little  pencil  dot  is  made  so  that  you 
may  start  from  the  same  point,  and  stop  at  that  point  so  as  to  read  closely.  The 
roller,  C,  after  having  adjusted  the  diagram  and  the  Planimeter  to  the  point 
from  which  you  are  to  start,  may  be  lifted  by  raising  the  joint  of  the  instrument 
slightly  from  the  paper,  so  that  the  0  on  the  wheel,  and  the  0  on  the  vernier, 

or  little  scale  attached  to  the 
joint  of  the  instrument,  shall 
coincide  with  each  other  pre- 
cisely. Then  take  the  tracing 
point,  B,  run  it  around  the 
diagram,  being  careful  to  fol- 
low the  line  exactly,  stopping 
at  the  same  point  from  which 
you  started.  Now,  to  get  at 
the  result,  you  must  make  a 
correct  reading.  In  our  case, 
we  started  at  0.  When  we 
stopped,  the  3  on  the  wheel, 
and  nine  of  the  divisions  be- 
tween 3  and  4,  have  passed 
the  0  on  the  vernier;  hence, 
we  read  3~,9~,  then  from  the 
cipher  on  the  vernier  we  count 
back  until  the  mark  of  the 
vernier  coincides  with  a  mark 
on  the  wheel,  —  which  is  3, — 
hence,  we  have  3.93,  and  that 
is  the  result  of  this  computa- 
tion. We  now  take  the  point, 
B,  and  travel  around  the  d'a- 
gram,  G  M,  once  more;  this 
time  we  get  7  as  having  passed 
the  0 ;  the  eighth  line  has  also 
passed  the  0;  then  we  count 
FlG-  59-  up  the  marks  on  the  vernier, 

and  find  that  the  eighth  mark  on  the  vernier  coincides  with  the  mark  on  the 
wneei.  Previously  we  had  3.93,  so  we  subtract  3.93  from  7.88.  This  time 
we  have  3.95.  Surely,  we  have  done  one  or  the  other  carelessly,  so  we 
repeat  it.  The  next  time  we  are  more  careful,  and  we  get  3.93.  This 
is  also  repeated,  until  we  are  satisfied  that  3.93  is  right.  In  reading,  we 
sometimes  come  across  curious  mistakes.  If  we  start  at  A,  the  corner  of 


TWENTY   YEARS    WITH  THE  INDICATOR.  97 

the  diagram,  G  M,  taking  hold  of  the  point  above  B,  at  that  end  of 
the  lever,  with  the  point,  A,  at  our  left  hand,  and  the  point,  B,  coming 
directly  toward  us,  the  diagram  being  slanting,  the  right  hand  toward  us  and 
the  left  hand  from  us,  taking  the  lever  A  in  the  diagram  as  a  straight  surface 
parallel  to  our  face ;  then  we  bring  the  point,  B,  in  the  direction  of  the  arrow 
in  the  diagram,  backward  from  where  the  Indicator  made  the  marks  when 
attached  to  the  engine.  We  come  down  the  admission  line,  work  to  the  left 
on  the  exhaust  line,  go  up  on  the  expansion  line  in  the  direction  of  the  arrow, 
and  come  back  to  A  again.  Now,  the  top  of  the  index  wheel  must  be  read  to 
the  left  of  the  0  in  the  vernier ;  that  is  to  say,  in  our  last  reading  we  have  the 
figure  7  on  the  wheel,  which  has  passed  the  0  on  the  vernier  to  the  left ;  the 
seventh  line  has  also  passed  the  first  line  on  the  vernier,  and  then  we  must 
count  upon  the  vernier  to  the  ninth  line,  or  until  we  find  a  line  upon  the 
vernier  which  exactly  corresponds  with  a  line  upon  the  wheel.  The  line  upon 
the  vernier  is  the  last  one  that  is  read.  Remember,  the  readings  on  the  vernier 
are  last,  and  that  the  numbers  on  the  wheel  must  be  read  to  the  left  of  the  0, 
when  the  instrument  is  properly  operated.  In  this  way  you  will  not  become 
confused,  and  your  results  will  not  negative  each  other,  making  confusion.  It 
is  not  necessary  to  set  the  roller  to  the  cipher  on  the  vernier ;  you  can 
commence  anywhere,  having  perfected  yourself  with  reading  the  instrument, 
just  as  you  can  a  clock  when  you  look  at  it.  It  is  better  to  use  a  small  pocket 
lens  in  reading  this.  The  marks  on  the  vernier  are  tenths  of  the  marks  on  the 
wheel.  The  marks  on  the  wheel  are  hundredths,  so  that  the  marks  on  the 
vernier  are  thousandths.  Anything  can  be  figured  or  computed  by  the  Plani- 
meter  as  well  as  an  Indicator  diagram,  and,  if  you  wish  to  test  it  carefully, 
take  a  piece  of  zinc,  and,  with  a  pair  of  dividers,  make  a  circle  exactly  one 
inch  in  diameter ;  then,  with  the  Planimeter,  measure  this  carefully,  and  you 
will  have  the  area  of  a  one-inch  circle,  if  you  have  drawn  the  line  right. 

Having  ascertained  that  the  area  of  G  M  is  3.93,  we  have  now  to  measure 
its  length,  and  here  is  where  beginners  frequently  make  an  error.  The  length 
of  the  Indicator  diagram  can  only  be  properly  measured  by  erecting  the 
vertical  lines,  B,  C,  and  to  do  this  we  use  the  steel  triangles,  placing  one  at  the 
base,  and  with  the  other  drawing  the  lines,  B,  C,  just  as  closely  as  we  can  to 
the  pencil  mark  actually  made  by  the  Indicator;  and  we  must  measure  the 
extreme  range  of  travel  of  the  instrument,  else  our  computation  is  incorrect 
and  unreliable.  It  does  not  matter  what  the  shape  or  form  of  the  lines  drawn 
by  the  Indicator,  follow  the  lines  made  by  the  Indicator,  and  this  gives  the 
power  transmitted.  Sometimes,  in  figuring  for  other  purposes,  we  have  to 
take  in  an  area  not  defined  by  the  Indicator.  In  measuring  the  diagram  of  a 
condensing  engine,  it  can  be  measured  in  either  one  of  two  ways.  That  por- 
tion which  is  above  the  atmospheric  line,  or  the  high  pressure,  can  be  measured 
separately,  to  see  what  is  being  done ;  and  that  which  is  below  the  atmospheric 
line  can  be  measured  to  see  what  the  condenser  is  doing ;  or,  if  you  simply 


98 


TWENTY  YEARS   WITH  THE  INDICATOR. 


wish  to  ascertain  the  amount  of  power  exerted  by  the  engine,  then  include 
the  whole  figure  above  and  below  for  obtaining  the  area  of  this  figure,  and 
we  think  the  process  has  been  carefully  described. 

The  next  point  is  to  reduce  it  to  something  which  shall  represent  power 
or  work.  In  this  case  we  have  3.93  on  the  Planimeter,  the  length  of  the 
diagram  is  4ff  inches,  the  decimal  for  ff  is  .7812.  We  will,  therefore, 
divide  3.93  by  4.7812  inches,  and  this  will  give  us  the  height  of  an  ordi- 

nate  which  will  make  a  rectan- 
gular form  that  will  represent 
precisely  the  area  of  the  dia- 
gram, G  M.  Dividing  3.93  by 
4.7812  gives  us  .821.  This  is 
a  decimal  of  an  inch.  As  the 
spring  with  which  we  are 
working  is  number  thirty,  or 
thirty  pounds  to  the  inch,  we 
multiply  the  height  of  the 
ordinate  by  thirty,  which  gives 
us  the  number  of  pounds  mean 
pressure  exerted,  which  is 
24.63.  This  process  is  the 
same  for  any  size  engine,  or 
any  number  that  may  be  had 
on  the  Planimeter,  and  to  sim- 
plify matters  in  our  own  prac- 
tice, whenever  we  are  figuring 
an  engine,  we  do  it  as  follows  : 
The  diameter  of  the  cylinder, 
reduced  to  square  inches  (see 
table  on  properties  of  steam), 
multiplied  by  the  number  of 
feet  per  minute,  divided  by 
33,000,  gives  us  what  we  term 
the  constant,  which  represents 
the  number  of  horse-power  ex- 
erted by  each  pound  of  mean 
pressure  upon  that  piston  at 
the  speed  which  is  given.  In 
this  case,  therefore,  the  following  formula  is  applied:  The  diameter  of  the 
piston  being  24  inches,  area  452-39  square  inches;  five  feet  stroke,  60  revo- 
lutions, make  600  feet  per  minute ;  33,000  pounds  one  foot  high  in  one 
minute  is  one  horse-power ;  hence,  452.39  X  600 -^  33>ooo  =8.22,  which 
represents  8.22  horse-power  for  every  pound  of  mean  pressure  which  the 


FIG.  60. 


TWENTY  YEARS    WITH  THE  INDICATOR.  99 

Planimeter  gives  for  any  diagram  upon  this  particular  engine  at  the  speed 
we  have  given.  Now,  as  we  have  24.63  pounds  mean  pressure,  multiply  24.63 
by  8.22  and  it  gives  202.4586  horse-power. 

The  rule  for  reducing  the  figure  of  the  Indicator  is  as  follows :  Get  the 
reading  of  your  instrument  accurately ;  where  but  slight  differences  exist,  take 
three  or  four  readings  and  average  the  result ;  divide  this  by  the  length  of  the 
card,  taking  care  to  include  the  extreme  length  of  any  variation.  When  this 
result  has  been  attained,  multiply  by  the  scale  of  the  spring  which  you  are 
using ;  this  gives  you  the  pounds  of  mean  pressure.  Multiply  the  pounds  of 
mean  pressure  by  the  co-efficient,  which  represents  the  number  of  horse-power 
of  each  pound  of  mean  pressure,  from  the  rule  given  above,  and  you  will  very 
materially  simplify  the  process  of  working  up  these  diagrams.  If  you  are  used 
to  logarithms  you  can  do  them  with  about  one-fifth  the  figures. 

The  question  is  frequently  asked  as  to  "what  shall  I  measure  in  other 
respects."  The  following  illustrations  will  answer,  as  examples,  but  the  rules 
which  we  have  given  above  will  apply  to  each  and  every  one,  changing  the 
figures  according  to  the  facts  as  they  exist,  observing  always  to  take  good  care 
of  the  decimals  and  whole  numbers.  In  Fig.  60  we  have  drawn  the  outline  of 
two  different  Indicator  diagrams,  embodying  radically  different  principles,  in 
order  to  show  what  may  and  must  be  done  with  the  Planimeter  whenever 
using  it.  The  diagram,  A  A,  which  is  purely  a  fanciful  one,  based  on  the  same 
steam  pressure  as  B,  is  drawn  for  the  purpose  of  showing  that  any  measure- 
ment made  is  taken  by  starting  the  perpendicular  line  at  the  extreme  point, 
D,  and  measuring  from  G  D.  Should  we  drop  the  horizontal  line  from  C  to 
C,  we  should  not  include  the  actual  length  of  the  figure  over  which  the 
Indicator  traveled.  In  the  diagram,  B  B,  it  will  be  seen  that  the  end  of  the 
expansion  line  falls  below  the  atmospheric  line,  making  the  loop,  F.  In 
running  the  Planimeter  over  the  outline  of  this  figure,  follow  the  lines  precisely 
as  the  steam  Indicator  left  them  upon  the  paper,  in  the  direction  of  the  arrows. 
Now  the  space,  F,  really  acted  upon  the  piston  of  the  engine  by  holding  it 
back.  The  Planimeter  deducts  this  space  from  that  above  the  line  in  such  a 
way  that  actual  pressure  upon  the  piston  only  is  given.  In  this  case,  we  must 
draw  the  vertical  line  from  E  to  E,  and  the  length  of  the  card,  B  B,  is  from 
H  to  E.  In  brief,  the  rule  for  the  action  of  the  Planimeter,  in  computing  areas, 
is  to  follow  the  outline  ©f  the  card  as  the  instrument  leaves  it,  without  any 
reference  to  ideas.  It  is  sometimes  a  question,  in  the  case  of  an  engine  with  a 
large  amount  of  back  pressure,  how  to  figure  it.  Take  the  area  of  the  figure 
bounded  by  the  instrument  which  gives  the  transmitted  power,  and,  if  you  are 
figuring  for  fuel,  or  desire  to  know  what  the  whole  power  exerted  by  the  steam 
is,  take  in  all  the  back  pressure,  as  in  the  diagram,  G  M.  The  line,  D,  in  this 
card,  is  an  imaginary  one,  and  represents  what  might  be  an  enormous  back 
pressure.  Now,  if  this  engine  is  exhausting  under  this  pressure,  E  being 
the  real  atmospheric  line  of  the  instrument,  and  D  the  supposed  line  of  back 


ioc  TWENTY  YEARS    WITH  THE  INDICATOR, 

pressure,  then  \ve  must  measure  the  area  between  E  and  D  for  fuel,  for,  as  a 
matter  of  fact,  the  boilers  furnish  the  steam  to  do  this  work  with,  but  the  work 
is  not  figured  in  because  it  is  spent  to  no  purpose.  The  power  is  consumed 
in  the  engine  itself,  and  is  not,  therefore,  transmitted  to  the  machinery 
beyond. 

The  use  of  the  Planimeter  does  not  require  a  particle  more  skill  than  does 
the  use  of  any  other  good  tool  about  the  mill ;  it  works  to  ten-thousandths  of 
a  square  inch  ;  it  is  a  delicate  little  instrument,  and  must  not  be  thrown  around 
like  a  pair  of  gas-pipe  tongs  or  a  blacksmith's  hammer.  A  very  little  puts  it 
out  of  order,  and  then  it  must  go  into  the  hands  of  some  man  who  can  put  it 
into  order  again.  We  have  one  of  the  large  ones,  which  we  have  carried 
probably  25,000  miles,  within  the  last  five  years.  It  never  has  been  out  of 
order  for  a  moment ;  it  is  as  perfect  as  the  day  we  bought  it,  eleven  years  ago, 
and,  if  it  is  not  abused,  will  be  good  twenty  years  hence.  An  Indicator  may 
be  properly  classed  in  exactly  the  same  category ;  it  is  expected  to  detect 
little  differences  or  discrepancies,  and  it  requires  to  be  handled  very  carefully. 
Either  instrument  is  as  serviceable  as  a  good  watch,  and  requires  just  about  the 
same  care  in  the  handling,  and,  if  they  are  well  used,  will  give  accurate  results 
every  time. 


LESSON   XXVIL 


THE  diagrams,  here  shown,  are  very  interesting  comparisons.  Diagram 
B  S  N,  Fig.  6 1,  is  from  a  Corliss  engine,  built  by  George  H.  Corliss,  in  1865, 
with  his  old  style  valve-tripping,  tripped  direct  by  the  governor,  closed  by 
springs,  20^  inches  diameter,  42  inches  stroke,  84  revolutions  per  minute,  100 
pounds  of  steam  in  the  boiler,  throttle-valve  wide  open.  The  parties  who  own 
this  valve,  write  as  follows :  "  Enclosed  is  diagram  from  our  engine,  as  it  was 
running  on  the  nth  of  March.  We  call  it  a  good  card."  In  response  to  an 
inquiry,  they  wrote  as  follows:  "Our  engine  has  very  variable  work.  At 
times  it  will  be  doing  more  than  300  horse-power,  and  instantly  drop  to  150, 
or  below,  and  the  governor  regulates  so  promptly  that  it  will  not  vary  a  turn 


TWENTY  YEARS    WITH  TH£ 


TOR. 


101 


when  the  changes  are  so  sudden  and  extreme.  We  have  bored  out  the  valve 
seats  twice,  and  put  in  one  set  of  new  valves  since  it  was  started.  It  had  poor 
management  in  early  life,  and  from  1865  to  1870  the  expenses  for  repairs,  cut- 
off attachments,  oil  pumps,  and  eccentric  arrangements,  were  large,  but  the 
trouble  arose  from  the  incompetency  of  the  mechanic  in  charge.  Since  the 
new  valves  were  put  in  —  four  years  ago  —  we  have  not  spent  one  hundred 
dollars  in  all  repairs  on  the  engine,  incident  to  her  regular  work.  We  run  ten 
hours  a  day,  and  from  305  to  306  days  in  each  year." 

Here  is  an  engine  that  was,  for 
the  first  five  years  of  its  life,  badly 
abused,  in  charge  of  an  incompetent 
man,  —  the  bill  of  expenses  for  re- 
pairs was  large,  —  but  since  the  new 
order  of  things  all  this  has  been 
radically  changed.  We  frequently 
hear  it  said,  —  mostly  by  parties 
who  are  interested  in  some  other 
style  of  engine,  —  that  the  Corliss 
engine  requires  reboring,  refitting, 
and  a  new  set  of  valves  every  few 
months,  or  weeks,  even,  but  we 
seldom  find  people  who  are  using 
them,  where  they  have  anything 
except  a  numskull  in  charge  of 
the  engine,  who  corroborate  any 
such  kind  of  a  statement  or  story. 
We  have  drawn  vertical  lines,  and 
find  that  this  engine  is  taking  its 
steam  very  nearly  right  ;  in  fact,  the 
admission  line  and  the  vertical  line 
are  so  near  together,  that  we  would 
not  advise  any  alteration  at  all. 
The  steam  line  of  the  engine  is 
very  good  indeed,  considering  its 
high  speed,  and  the  amount  of 
work  it  is  doing.  With  one  hun- 
dred pounds  in  the  boiler,  we  get 
92  pounds  at  A  B.  The  steam 
line  on  the  head  end  is  hardly  as  good  as  on  the  crank  end,  and  it  falls,  before 
cutting  off,  ten  pounds,  from  the  initial  pressure  realized  in  the  cylinder. 
The  expansion  lines  are  very  good  ;  the  only  change  we  would  suggest,  would 
be  the  opening  of  the  exhaust  valve  at  C,  D,  making  the  dotted  line  down  to 
the  atmospheric  line  of  the  instrument,  so  as  to  save  the  little  back  pressure 


102  TWENTY  YEARS    WITH  THE  INDICATOR. 

upon  the  return  of  the  piston.  This  would,  undoubtedly,  make  a  little  more 
compression,  and  would  make  the  engine  run  fully  as  quietly  as  now.  Practi- 
cally, the  diagrams  are  first-rate,  better  than  the  average,  which  only  goes  to 
prove  that  the  Richards  Indicator,  with  which  they  were  taken,  with  a  40 
spring,  is  reliable,  when  kept  in  good  order ;  and  we  believe,  with  proper  care, 
it  will  take  a  steam  engine  up  nicely  to  a  speed  of  one  hundred  revolutions. 
The  diagrams  in  question  were  taken  with  a  three-way  cock,  and  are  of  no 
value  in  the  adjustment  of  one  end  with  the  other. 

In  contrast  with  diagram  B  S  N,  we  publish  diagram  H  E  W,  from  an 
engine  which  has  been  running  30  years,  old  fashioned  slide  valves,  cutting  off 
at  half  stroke.  The  cylinder  has  never  been  rebored.  It  is  20  inches  in 
diameter,  4  feet  stroke,  55  strokes  per  minute;  boiler  pressure  75  pounds; 
mill  heated  by  exhaust,  as  also^the  wash  room  and  dye  room  of  the  concern 
from  which  this  was  taken.  The  scale  of  the  diagram  was  44  pounds  per 


HEW 


FIG.  62. 


inch.  Fifty-five  pounds  of  the  boiler  pressure  is  put  upon  the  head  of  the 
piston,  cutting  off  at  about  one-third  stroke.  Six  pounds  is  lost  at  the  cut  off 
from  the  pressure  realized  at  the  commencement  of  the  stroke.  The  expan- 
sion line  is  somewhat  wavy,  and  the  back  pressure  is  not  excessive,  when  it  is 
considered  what  an  amount  of  work  the  engine  is  doing.  While  this  engine 
is  not  among  the  most  economical  motors  of  the  day,  it  is  an  example  of  old 
style  engineering,  which  is  capable  of  doing  lengthy  service  with  reasonable 
economy.  We  are  not  informed  as  to  the  amount  of  fuel  used  for  the  power. 
It  will  not,  however,  compare  with  the  economy  of  diagram  B  S  N.  At  the 
same  time,  diagram  H  E  W  is  a  vast  improvement  over  engines  built  in  its 
day,  some  of  which  are  now  running.  We  have  hardly  the  data  at  hand  for 
comparing  the  relative  efficiency.  We  would  not  advise  the  purchase  of  an 
engine  of  this  class,  from  an  economical  stand-point,  and  yet,  some  of  them  are 
doing  fully  as  good  work,  for  the  pounds  of  coal  consumed,  as  modern  engines 
not  built  upon  the  right  principles. 


TWENTY  YEARS    WITH  THE  INDICATOR.  103 


LESSON   XXVIII. 


THE  object  of  the  diagrams  in  this  lesson  is  to  illustrate,  as  the  acquaint- 
ance with  the  Indicator  extends,  some  little  occasionals  that  will  persist  in 
cropping  up,  and  not  always  to  the  pleasure  or  profit  of  the  party  who  is 
operating  the  instrument.  These  diagrams  are,  for  the  sake  of  convenience, 
traced  upon  the  same  block.  As  they  are  both  from  actual  occurrences,  which 
are  liable  to  occur  at  any  time,  we  have  made  them  the  subject  of  this  lesson. 
The  Indicator  is  a  delicate  instrument,  and  requires  care;  it  also  requires, 
what  good  printers  have  to  mix  with  their  ink  to  get  nice  work  —  a  little 
brains  and  practice  in  the  use  of  it.  The  card,  A,  Fig.  63,  is  taken  from  a 
Richards  instrument  on  a  Corliss  engine.  The  engineer  discovered,  all  at 
once,  that  the  Richards  Indicator  was  not  reliable,  and  he  made  this  discovery 
by  the  help  of  a  gentleman  who  was  very  strongly  prejudiced  in  favor  of 
another  Indicator ;  and  this  gentleman,  who  was  educating  the  engineer,  forgot 
entirely  to  tell  him  that  possibly  his  Indicator  might  be  out  of  adjustment, 
even  if  he  knew  it  himself;  so  the  engineer  was  writing  for  advice  regarding 
whose  instrument  he  should  buy,  and  the  diagrams  came  to  us  through  the 
mail.  Now,  if  our  readers  will  pay  attention,  some  of  them  may  know  imme- 
diately what  is  the  trouble  when  they  see  this  thing  repeated.  Starting  at  A, 
or  at  the  termination  of  the  exhaust  and  commencement  of  compression,  we 
notice  that  the  line  is  heavy ;  it  gradually  comes  to  be  dots,  and  the  dots  are 
further  apart,  —  there  is  no  steam  line,  —  and,  after  the  expansion  has  begun, 
it  starts  in  again  with  dots,  and  finally,  after  some  time,  makes  a  heavy  line 
again,  and  at  A,  on  the  expansion  curve,  comes  down  to  about  the  right  sized 
line  again.  Now  this  instrument  was  a  Richards,  made  several  years  since. 
We  wrote  the  engineer  to  please  send  us  his  instrument,  and  thought  we  could 
tell  him  where  the  trouble  was.  Upon  our  applying  the  instrument,  it  did  not 
take  over  twenty  seconds  to  find  the  whole  trouble.  The  piston  barrel  is 
surrounded  by  a  casing,  and  the  paper  cylinder  is  held  in  place  by  a  short 
bar.  The  stand  which  surrounds  the  piston  casing  of  the  instrument  had 
been  thumped,  and  the  bar  had  been  sprung  so  that  the  top  of  the  paper  barrel 
was  further  away  from  the  top  of  the  piston  than  the  bottom  of  it.  Conse- 
quently, when  we  fastened  the  pencil  to  the  bar,  it  made  a  heavy  mark  at  the 
bottom,  and  made  no  mark  at  all  at  the  top.  In  other  words,  the  paper 
cylinder  was  out  of  parallel  with  the  piston  rod  of  the  instrument.  Sometimes 
the  cylinder  gets  sprung  exactly  the  other  way,  so  that  there  will  be  a  heavy 
mark  at  the  top  and  none  at  the  bottom.  A  little  readjustment  and  correcting 


io4  TWENTY  YEARS    WITH  THE  INDICA  TOR. 

of  the  springs,  —  which  had  been  used  a  number  of  years,  — and  after 
loosening  the  nuts  in  the  heads  of  the  springs,  we  put  the  instrument  back 
again  upon  the  engine,  and  it  made  elegant  diagrams,  so  much  so,  that  on  its 
return  the  engineer  decided  that  he  did  not  know  all  there  was  about  an 

Indicator,  although  he  had  been  using  it 
a  number  of  years  ;  and,  instead  of  buy- 
ing a  new  instrument,  concluded  that  a 
reliable  instrument  would  answer  just  as 
well.  This  is  a  thing  that  not  infre- 
quently happens.  We  have  seen  parties 
lay  an  instrument  down  upon  a  bench,  or 
hit  it  carelessly  against  a  weight,  shaft, 
or  something,  and  then,  for  the  next 
three  months,  grumble  about  their  Indi- 
cators having  given  out,  or  got  out  of 
order,  when,  as  a  matter  of  fact,  a  little 
carelessness  put  the  instrument  out  of 
shape,  and  lack  of  patience,  or  pains  in 
ascertaining  just  where  the  trouble  was, 
kept  them  from  realizing  their  folly  or 
ignorance. 

In  card  B,  Fig.  63,  we  have  quite 
another  case,  yet  not  a  particle  less  inter- 
esting or  less  profitable.  In  this  case, 
the  compression  line  will  be  found  to  be 
dotted ;  the  steam  line  is  very  good,  but 
the  expansion  line  —  the  upper  portion 
of  it — is  anything  but  good,  and  it 
finally  drops  away  into  dots ;  and  down 
on  the  expansion  line,  B,  there  is  a 
sudden  falling  off,  and  a  very  erratic 
continuation  of  the  expansion  line.  This 
is  a  peculiar,  but  by  no  means  impossible 
diagram,  and,  if  our  readers  will  draw  a 
line  parallel  with  the  atmospheric  line  of 
the  instrument  on  the  diagram,  they  will 
find  that  the  dots  commence  at  about  the 
same  height  from  the  parallel  line  at  both 
FlG-  63-  ends  of  the  card ;  in  other  words,  that 

the  dots  on  the  compression  or  admission  line,  and  on  the  expansion  lines, 
commence  at  just  about  the  same  height  from  the  atmospheric  line  in  both 
cases.  This  can  hardly  occur  from  any  action  of  the  steam  in  the  cylinder. 
The  party  who  sent  this  diagram  took  it  from  the  Thompson  instrument^  and 


TWENTY  YEARS    WITH  THE  INDICATOR.  105 

he  declared  his  belief  that  the  Thompson  instrument  was  not  over  half  made. 
We  requested  him  to  send  it  to  us,  which  was  promptly  done.  Somebody, 
who  had  been  trying  to  handle  it,  had  bent  the  piston  head  on  the  end  of  the 
rod  in  one  direction,  and  had  sprung  the  piston  exactly  in  the  other  direction. 
When  the  bend  in  the  piston  rod,  or  shell  which  surrounds  the  connection 
with  the  parallel  motion  above,  came  through  the  bearing  in  the  top,  it 
necessarily  bound,  although  but  slightly,  and  .the  pencil  jumped.  The  steam 
line  is  straight,  or  nearly  so,  for  the  best  of  reasons :  the  piston  of  the  instru- 
ment was  at  that  moment  standing  still,  the  pressure  being  so  nearly  uniform. 
When  it  starts  to  descend,  it  makes  a  very  fine  cut  off,  but  after  it  descends  an 
eighth  of  an  inch,  then  the  trouble  commences  by  the  piston  beginning  to  stick, 
and  sticking  worse  until  it  makes  dots.  Beyond  the  letter  B,  on  the  expansion 
line,  where  the  jog  is  marked,  it  drops  off  instantly,  and,  if  the  curve  is 
applied,  the  expansion  line  at  this  point  will  be  found  too  high.  Up  to  this 
time,  the  pressure  in  the  cylinder  was  nearly  enough  to  help  the  bend  in  the 
piston-rod,  but,  when  the  steam  became  thoroughly  expanded,  then  the  piston 
went  down  with  a  jump,  and  the  line  beyond  it  shows  exactly  how  it  worked. 
Upon  a  careful  examination  of  this  Indicator,  the  bend  was  found  to  be  very 
small,  but  was  just  as  essential  as  though  it  had  been  bent  double.  The  piston 
was  sent  back  and  reorganized,  a  new  piston  put  into  the  instrument,  and 
some  of  the  most  elegant  cards  taken  at  the  first  trial.  Upon  returning  the 
Indicator  to  our  inquirer,  he  wrote  briefly,  saying,  "  I  believe  that  the  Thomp- 
son Indicator  is  well  made,  and  that  I  am  a  good  deal  nearer  a  blockhead  than 
anything  else.  Please  don't  give  this  away,  and  the  next  time  I  am  stuck  I 
shall  know  where  to  send." 

Now  these  cases  are  possible.  It  does  not  do  to  p'ut  your  Indicator  in  a 
vise  in  order  to  get  at  any  unscrewing  of  the  parts ;  it  must  not  be  run  by 
tallow  or  cylinder  oil  blown  into  the  piston,  for  the  piston  was  not  made  to 
work  in  that  kind  of  material  any  more  than  in  a  sand  bank ;  it  requires,  at 
times,  a  little  patience,  and  makes  a  good  deal  of  annoyance,  as  we  have  often 
found,  at  the  expense  of  burnt  fingers  and  abraded  knuckles ;  but  impatience, 
and  getting  out  of  sorts,  don't  make  the  Indicator  work  better,  and  it  does 
frequently  get  a  man  into  a  complete  tangle.  It  makes  no  difference  how 
much  pains  the  maker  of  the  instrument  takes  in  its  adjustment,  the  machine 
must  be  used  as  a  machine,  and  as  a  very  intelligent  one. 


io6  TWENTY  YEARS    WITH  THE  INDICATOR 


LESSON   XXIX. 


THE  different  classes  of  engines  in  use  show,  to  the  investigator,  peculiar 
vagaries  and  radical  departures  from  either  the  theoretical  or  practical,  so  far 
as  economy  is  concerned.  At  the  same  time,  men  have  peculiar  ideas,  and 
frequently  indulge  themselves  in  experiments  which,  sooner  or  later,  develop 
into  such  peculiar  looking  objects  as  we  have  for  the  subject  of  this  lesson. 
We  have  had  much  to  say  and  do  with  the  rotary  valve,  and  now  we  have  a 
fixed  slide  valve,  or,  as  it  is  usually  spoken  of,  a  plain  slide  valve,  in  which 
case  there  is  no  cut  off  beyond  that  limited  by  the  carrying  of  the  steam.  The 
four  sets  of  cards  shown  represent  four  different  engines;  we  might,  with 
perfect  propriety,  say  four  abortions  in  the  use  of  steam.  A  little  explanation 
will  show  that  each  one  of  these  was  an  attempt  to  work  out  somebody's  ideas 
in  the  use  of  steam. 


FIG.  64. 

Diagrams  A,  Fig.  64,  is  what  is  termed  a  rotary-plug  valve,  scale  40,  and 
it  might,  perhaps,  puzzle  some  of  our  readers  to  ascertain  which  was  the 
steam  end,  and  which  the  exhaust  end  of  the  diagram.  Both  diagrams  are 
given,  but  the  subject  is  hardly  worth  more  space  than  we  have  now  given  it. 
The  scale  is  40,  and  the  base  line,  or  lower  line  in  the  card,  is  the  line  of  rest, 
or  the  atmospheric  line  of  the  instrument.  The  man  who  arranged  this  did 
not  believe  in  clap-trap  valve-gears,  and  he  succeeded  in  making  his  own  vaive 
gear  work.  To  use  a  little  quotation,  "  No  need  of  such  nonsense ;  we  can 
make  a  simple,  cheap  engine  that  will  work  just  as  economically  as  any  of 
them."  Strange  as  it  may  seem,  this  man  really  had  the  good  sense  to  make 
use  of  the  Indicator,  and  he  was  very  soon  converted  to  a  clap-trap  valve 
gear.  We  don't  wonder  that  he  was. 

Diagrams  B,  Fig.  65,  show  what  may  occur  to  the  plain  slide-valve 
engine  when  the  eccentric  slips  from  one-quarter  to  one-third  of  its  way  on 


TWENTY   YEARS    WITH  THE  INDICATOR. 


107 


the  main  shaft.  The  steam  and  exhaust  are  very  late,  and  this  engine  would 
make  first-rate  junk,  and  would  be  cheaper  in  the  junk  pile  than  in  the  engine 
room  if  it  had  to  work  in  this  way. 


FIG.  65. 

Diagrams  C,  Fig.  66,  are  a  curiosity  in  the  literature  of  engineering.  The 
engine  was  moderately  well  constructed,  the  steam  line,  as  shown,  is  very  fair, 
the  exhaust  commences  to  open  at  about  the  right  place,  but  it  never  gets 
open  enough  to  get  rid  of  the  back  pressure.  But  the  trouble  in  this  case  is 
not  in  the  engine,  it  was,  rather,  in  the  vague  ideas  of  a  man  who  did  not 
believe  in  heating  his  mill  by  direct  steam.  He  was  going  to  economize  his 
exhaust.  His  train  of  argument  was  something  like  this :  "If  my  exhaust 
steam  can  be  carried  through  a  long  pipe,  I  can  extract  all  the  heat  from  it, 
and  save  what  would  otherwise  be  thrown  away."  Not  satisfied  with  this,  he 
had  another  exceedingly  happy  thought:  having  used  a  considerably  long 


FIG.  66. 


circuit,  he  kept  reducing  the  size  of  the  pipes  for  fear  that  one  or  two 
extra  degrees  of  heat  might  escape  his  grasp,  until,  finally,  what  little  heat 
there  was  left  in  the  steam,  was  made  to  escape  through  a  three-quarter  inch 
pipe,  and  a  tank  of  water.  The  diagram  shows  that  he  made  a  brilliant 
success  in  one  respect,  and  a  brilliant  failure  in  the  other.  He  probably 
succeeded  in  extracting  all  the  heat,  but  at  a  slight  expense  in  fuel.  The 
figures  show  the  reading  of  the  Planimeter.  It  will  be  seen  that  the  effective 
work  yielded  was  238  out  of  773.  In  other  words,  it  required  773  horse- 
power, if  you  choose,  to  develop  238  horse-power,  transmitted  to  the 


io8  TWENTY   YEARS    \VITH   THE  INDICATOR. 

machinery,  238  horse-power  being  yielded  by  the  belting,  and  435  horse- 
power being  consumed  in  pushing  the  steam  out  of  the  cylinder,  through 
several  miles  or  less  of  pipe,  into  a  tank  of  water.  While  the  amount  of 
power  in  this  case  is  largely  exaggerated,  the  actual  proportions  are  precisely 
as  stated.  He  did  heat  the  rooms,  and  he  did  squeeze  the  last  item  of  heat 
out  of  the  steam ;  which,  in  turn,  revenged  itself  upon  him  in  his  fuel  bill,  as 
any  sensible  man  would  long  before  have  discovered.  At  the  commencement 
of  this  operation  he  congratulated  himself.  We  can  imagine  him  rubbing  his 
hands  with  glee,  but  when  the  fuel  bills  began  to  come  in,  his  face  grew  as  long 
as  a  broomstick ;  he  wondered  somewhat,  after  a  little  time  wavered,  then 
doubted  his  own  success,  and,  as  a  last  resort,  called  in  the  doctor ;  and  we 
will  let  him  down  easy,  by  saying  tha<-  he  now  uses  direct  steam  for  heating 
his  mill,  runs  his  exhaust  steam  through  a  heater,  and  takes  very  great  pains 
that  his  heater  has  an  extravagantly  good  amount  of  exhaust  room,  that  the 
steam  is  not  choked  anywhere,  and  looks  out  for  sharp  turns  in  every  direc- 
tion ;  and  he  is  not  only  a  converted  man,  in  the  strictest  sense  of  the  word, 
but  is  richer,  both  by  experience  and  in  his  pocket.  Heating  by  exhaust 
steam  is  a  great  hobby  with  some  people,  and  others  who  have  tried  it  have 
found  that  it  is,  unless  properly  managed,  very  expensive ;  in  fact,  so  much  so, 
that  many  concerns  have  abandoned  it,  preferring  to  heat  their  feed  water,  and 
then,  having  economized  in  a  sensible  way,  they  can  well  afford  to  make  more 
steam,  and  send  it  around  by  direct  circulation.  It  hardly  pays  to  heat  by 
exhaust  steam  when  it  troubles  the  power  of  the  engine,  and  this  party  referred 
to  above  was,  no  doubt,  an  unbeliever  in  the  utility  of  Ihe  Indicator,  until  he 
was  converted  by  main  force.  In  other  words,  it  required  him  to  bring  his 
skull  in  contact  with  a  stone  in  order  to  set  him  thinking. 


FIG.  67. 

Diagrams  D,  Fig.  67,  represent  an  experiment  upon  an  elal orate  scale,  by 
an  engine  builder,  and  a  man  of  some  considerable  experience,  who  really 
made  a  pretence  of  building  a  good  engine.  This  man  also  had  a  hobby.  It 
was,  that  the  impact  of  the  steam  upon  the  piston  head  was  tremendous,  and 
that,  instead  of  doing  the  work  as  it  should,  by  attempting-  it  in  that  way. 
continually  tore  the  engine  to  pieces,  or  set  it  to  thumpin?  and  pounding — 


TWENTY  YEARS    WITH  THE  INDICATOR.  109 

so  he  had  a  brilliant  idea.  As  the  impact  of  the  entering  steam  was  altogether 
wrong,  and  could  not  do  any  work,  for  the  crank  was  on  the  centre,  he 
concluded  that  the  time  for  the  action  of  full  pressure  was  in  the  middle  of 
the  stroke,  as  he  believed  in  putting  the  steam  where  it  would  do  the  most 
good.  'He  constructed  his  ports  and  valves  to  work  as  these  diagrams  show. 
He  believed  he  had  the  philosopher's  stone  and  the  true  theory  of  steam 
distribution,  and  either  his  engine,  or  one  of  the  high  speed  engines,  must  fall. 
His  conversion  was,  perhaps,  as  forcible  as  the  engine.  He  admitted  steam 
gradually  at  first.  (The  diagrams  are  taken  wjth  a  40  spring.)  It  will  be  seen 
that  the  steam  raised  in  the  middle,  struck  to  the  highest  pressure,  takes  a  back 
lash  before  it  gets  ready  to  exhaust,  and  really  bears  a  very  fair  analogy  to  the 
shape  of  a  sperm  whale's  head.  The  figure  is  a  literal  representation  of  the 
obtuseness  of  this  man,  who  afterward  found  that  there  was  a  good  deal  of 
difference  between  tweedle-dee  and  tweedle-dum. 

There  is  nothing  good  to  be  said  of  any  of  these  diagrams,  yet  they  are 
not,  by  any  means,  the  worst  that  could  be  produced.  Taken  as  a  class,  A 
and  B  are  fair  representations  of  what  is  being  done  regularly,  while  C  and  D 
are  monstrosities,  and  are  of  no  more  practical  use,  or  real  practical  value, 
than  a  wooden  man  would  be  as  engineer.  We  have  given  them,  not  because 
they  conveyed  valuable  instruction  to  our  engineers,  but  for  the  reason  that 
this  lesson  is  intended  more  for  steam  users  and  for  some  of  those  parties  who 
belong  either  to  the  chronic  or  constitutional  grumblers.  We  know,  person- 
ally, where  there  are  engines  running  worse  than  either  of  the  four  cards,  and 
not  five  miles  from  where  we  are  now  writing. 


LESSON  XXX. 


THE  diagrams  for  this  lesson  are  both  from  men  who  are  running  engines. 
Diagrams  A,  Fig.  68,  are  from  an  engine  manufactured  by  the  Hartford 
Engineering  Company,  of  Hartford,  now  in  operation  in  a  New  England 
cotton  mill.  The  data  which  comes  to  us  is  not  complete.  Steam  72,  scale 
30,  revolutions  124  per  minute.  The  steam  line  is  very  good  indeed.  The 
cut  off  of  this  engine  is  closely  defined ;  the  expansion  line  would  seem  to  be 


no  TWENTY  YEARS    WITH  THE  INDICATOR. 

very  good,  but,  as  the  clearance  is  not  given,  we  cannot  state  definitely  what 
its  approximation  is  to  the  so-called  theoretical  curve.  The  exhaust  valve 
upon  either  end  opens  early  at  A,  and  the  back  pressure  is  very  small.  We 
have  no  means  of  knowing  whether  the  steam  is  being  exhausted  into  the 
open  air,  or  is  being  used  for  heating.  At  any  rate,  the  back  pressure  is  less 
than  two  pounds.  The  compression  lines  made  by  the  valves  of  this  machine 
require  less  length  of  stroke,  and  approximate  to  steam  pressure  nearer  than 
that  of  the  generally  constructed  high-speed  engines.  In  other  words,  there 
is  less  compression  in  volume  as  regards  the  proportion  of  compression  to  the 
whole  length  of  the  stroke,  and  the  compression  is  made  effective  by  what 
appear  to  be  close  working  valves.  The  engine  falls  about  ten  pounds  short  of 
boiler  pressure ;  but,  unlike  most  high-speed  engines,  the  steam  line  does  not 
drop  off  ten  pounds  from  the  pressure  first  realized  on  the  piston.  The  falling 
off  of  the  steam  line  from  the  first  impact  is  not  appreciable,  in  fact,  cannot 


FIG.  68. 


be  measured  by  the  scale  used.  It  is  rather  a" matter  of  regret  that  more  data 
did  not  accompany  the  card.  The  valves  would  seem  not  to  be  leaking ;  their 
action  is  proportionately  the  same ;  the  expansion  line,  we  have  little  doubt, 
will  approximate  very  nearly  the  curve ;  and  yet,  much  of  this  depends  on  the 
condition  of  the  steam,  and  the  distance  of  the  engine  from  the  boilers ;  but, 
taking  it  precisely  as  it  reaches  our  hand,  it  is  a  very  good  diagram.  This 
engine  must  not  be  confused  with  what  is  known  as  the  Buckeye  engine, 
built  in  the  West.  This  is  peculiarly  an  Eastern  machine,  and  is  very  far 
superior  to  any  cards  we  have  ever  seen  taken  from  the  Ohio  machine. 

Diagrams  C  F,  Fig.  69,  come  to  us  all  the  way  from  St.  Louis,  and  is 
from  the  Reynolds-Corliss  engine,  built  by  Allis  &  Co.,  of  Milwaukee,  Wis. 
The  data,  which  comes  with  this  diagram,  is :  Diameter  of  cylinder  28  inches, 
length  of  stroke  5  feet,  revolutions  63,  spring  40,  boiler  pressure  75.  The 
peculiar  feature  of  this  engine  is  its  beautiful  compression  lines  and  the  close 


TWENTY  YEARS    WITH  THE  INDICATOR. 


in 


expansion  line.  The  steam  pressure  is  very  nearly  the  same,  falling  nearly  ten 
pounds  from  boiler  pressure.  The  dotted  lines  over  the  steam  line  would  lead 
us  to  suppose,  not  having  the  facts  in  our  possession,  that  the  steam  was  either 
drawn  some  ways  from  the  boiler,  or  else  through  a  pipe  that  was  hardly  large 
enough  to  supply  the  demand  made  by  the  opening  of  the  steam  valves.  It 
will  be  noticed  that  the  head  end  falls  off  more  radically  than  the  crank  from 
the  steam  line  or  induction  pressure,  and  this  fact  would  give  us  the  rounding 


FIG.  69. 

over  of  the  corner  from  the  fact  of  the  steam  valves  closing  on  a  deficient 
supply  of  steam,  so  that  the  steam  is,  to  a  certain  extent,  wire  drawn  through 
the  valve  after  it  commences  to  close,  and  this,  in  fact,  is  the  only  poor  feature 
of  this  diagram.  Judging  from  the  appearance  of  the  cards,  we  should  say 
that  the  engineer  in  charge  had  some  pride  in  his  engine,  and  was  endeavoring 
to  see  how  well  he  could  do  with  it,  rather  than  how  much  he  could  get  out  of 
it.  Both  these  cards  were  taken  by  the  engineers  themselves. 


LESSON   XXXI. 


A  PRACTICAL  illustration  of  the  value  of  the  Indicator  could  not  be  more 
forcibly  made  to  the  mind  of  any  man,  who  is  capable  of  reasoning,  or  one 
who  is  not  prejudiced,  than  the  one  which  is  here  presented.  We  frequently 
receive  inquiries  as  to  peculiar  points  of  working,  some  of  which  cannot  be 
explained  satisfactorily  without  a  careful  investigation,  and  others  which  can 


112 


TWENTY   YEARS    WITH   THE  INDICATOR. 


never  be  remedied  until  after  the  faults  which  are  left  by  the  builder  in  the 
machine  are  all  removed. 

In  order  to  save  space,  and,  at  the  same  time,  to  make  the  lesson  all  the 
more  forcible,  we  have  drawn  two  sets  of  diagrams  upon  the  same  block.  The 
disproportion  in  the  outlines  which  follow  each  other  can  be  studied  by  any 
one  who  is  interested.  Briefly  stated,  the  case  is  as  follows :  Some  time  ago, 
the  writer  of  this  was  called  to  look  at  an  engine  just  outside  the  City  of 
Boston.  The  engineer  did  not  believe  in  Indicators,  and  considered  that  any 
man  who  attempted  to  meddle  with  the  engine,  after  he  had  placed  it  where 
it  should  run,  had  taken  in  a  "  pretty  fat  job,"  to  use  exactly  his  own  words. 
However,  the  engines  were  adjusted,  although  but  one  of  a  pair  was  generally 
used.  After  he  saw  how  easy  it  was  to  control  the  movement  of  the  engine, 
and  to  bring  everything  into  working  order,  he  became  very  much  interested 
in  the  Indicator,  and  the  agent  of  the  concern  ordered  a  set,  with  which  the 
engineer  is  now  very  greatly  interested,  and  is  keeping  close  track  of  his 
engine.  The  engines  were  carefully  adjusted,  and,  as  some  changes  were 


FIG.  70. 

going  on  at  the  time  of  our  visit,  we  advised  the  changing  of  the  main  steam 
pipe  leading  to  the  engine.  As  some  especial  piece  of  casting  had  to  be 
procured,  it  was  not  done  at  the  moment.  So  we  were  somewhat  surprised,  a 
short  time  afterward,  to  receive  a  pair  of  diagrams,  one  taken  at  either  end 
of  the  cylinder,  on  the  same  stroke,  of  which  A  A  are  almost  absolutely  exact 
reproductions,  together  with  a  note  from  the  agent,  saying  that  there  was  some 
trouble  with  the  engine,  but,  as  nothing  had  been  changed  that  they  were 
aware  of,  he  could  not  explain,  nor  could  the  engineer,  why  they  should  make 
such  cards ;  would  we  telegraph  him,  the  instant  we  received  his  letter,  what 
to  do?  Here  was  a  puzzle.  The  crank  end  is  the  same  for  each  diagram,  in 
general,  at  least,  but  the  disproportion  between  the  head  and  crank  dotted 
line  is  rather  too  far  out  for  general  use.  The  other  engine  was  disabled.  He 


TWENTY  YEARS    WITH   THE  INDICATOR.  113 

had  worked  all  day  Monday  in  trying  to  get  at  the  matter,  so  that  our  letter 
was  received  Tuesday  morning.  We  telegraphed  him  at  once  to  take  off  the 
head  end  of  the  cylinder  and  see  if  there  was  anything  jammed  into  the  port, 
or  if  the  valve  was  free  in  its  working.  After  two  or  three  hours,  back  came 
his  answer :  "  Port  all  clear ;  will  be  ready  to  run  in  half  an  hour.  What  shall 
we  do  next  if  the  card  don't  improve?"  Away  went  our  answer:  "  If  the 
same  difficulty  still  exists,  pull  off  the  new  valve  and  see  if  there  is  anything 
in  the  steam -way  so  that  the  valve  don't  get  steam ;  if  this  don't  cure  it,  I  will 
be  there  at  five  o'clock."  This  left  our  office  about  eleven  o'clock.  At  four 
four  o'clock,  P.  M.,  came  another:  "No  improvement  on  taking  off  the 
cylinder  head;  we  followed  directions,  and  dug  out  a  blacksmith's  shop;  just 
connected  up,  and  everything  is  lovely  and  on  the  top  shelf."  Next  morning's 
mail  brought  us  along  a  laughable  letter,  enclosing  diagrams  B  B,  showing  the 
boiler  pressure  at  C  C,  scale  40,  engine  60  X  23,  running  56  revolutions.  The 
end  of  this  letter  was  about  as  follows :  "  If  there  is  a  man  in  this  country, 
today,  that  swears  by  the  Indicator,  it  is  your  old  friend,  our  engineer,  but  he 
thinks  that  a  little  Indicator,  some  telegraph,  and  some  common  sense,  work 
in  pretty  well  together."  Herewith  follows  an  explanation.  The  joke  of  the 
matter  was,  that  he  threatened  to  send  us  the  whole  batch  of  stuff  taken  out 
of  the  steam  passage  between  the  main  valve  and  the  steam  valves. 

"  When  the  new  steam  pipe  and  valve  arrived,  our  master  mechanic,  who 
usually  has  charge  of  these  things,  joked  the  engineer  about  his  not  loving 
that  '  feller '  who  came  out  with  the  Indicator.  They  had  some  good-natured 
chaff,  and  when  it  came  stopping-time  at  night,  the  master  mechanic,  thinking 
to  make  some  of  his  tools  all  safe,  put  a  large  lump  of  copper,  a  short  stub 
wrench,  an  S  wrench,  and  a  piece  of  lead,  which  he  had  been  using,  into  the 
steam  chest  of  the  engine.  The  next  morning  the  master  mechanic  was  called 
to  another  part  of  the  yard,  and,  before  leaving,  sent  one  of  the  men  to  the 
engine  room,  expecting  to  join  him  in  a  few  moments.  Being  bothered, 
himself,  by  something  which  demanded  his  attention,  the  engineer  and  his 
assistant,  being  in  a  hurry  to  get  that  mill  started,  helped  machinist  number 
two  to  lift  the  big  valve  in  its  place,  and  then  they  had  a  hunt  after  the 
wrenches,  —  not,  however,  finding  them.  Others  were  procured,  the  valve  was 
put  on,  the  gaskets  placed,  and  everything  screwed  up  for  '  keeps.'  Steam 
was  then  put  on,  and  the  engine  started  slowly  to  see  that  everything  was  all 
right.  The  result  you  have  in  the  cards.  The  joke  of  the  whole  thing  is 
that,  by  changing  the  men,  one  had  forgotten  about  his  tools,  and  the  other 
knew  nothing  of  it,  so  that  we  were  all  day  digging  out  our  machine  shop. 
The  lesson  has  not  been  without  good  results,  and  if  our  master  mechanic  is 
easily  nettled  now  by  reference  to  his  new  tool  chest,  you  can  imagine  why  he 
appreciates  the  joke.  The  engineer  in  turn  laughs  at  the  mechanic,  who  had 
previously  chaffed  him  (the  engineer)  about  the  Indicator  affair,  by  threatening 
to  take  out  a  patent  for  his  new  tool  chest." 


ii4  TWENTY  YEARS    WITH  THE  INDICATOR. 

Our  readers  have  here  a  stubborn  fact,  and  an  expensive  one,  but,  at  th^ 
same  time,  a  very  instructive  one.  The  diagram,  A,  head,  shows  conclusively 
that  the  steam  is  shut  away  from  the  piston  by  some  reason  or  other.  Some- 
times tools  have  been  clogged  in  the  port,  but  we  do  not  know  that  the  passage 
was  ever  before,  in  our  own  experience,  blocked  up  back  of  the  port.  A  lump 
of  copper,  five  and  one-half  or  six  inches  long  and  more  than  two  inches  in 
diameter,  and  a  piece  of  lead  as  big  as  two  ordinary  fists,  cover  a  large 
proportion  of  the  length  of  the  steam  port.  Come  to  mix  these  up  with  a 
stub  wrench,  made  from  inch  and  a  half  iron,  and  some  other  little  matters, 
which,  fortunately  for  the  valve,  were  so  placed  by  the  blast  of  steam  that  they 
did  not  pass  over  the  valve  and  catch  between  the  valve  and  the  port,  or  they 
would  have  made  music,  and  an  expensive  bill  of  repairs,  and  effectually  shut 
the  steam  away  from  the  head  valve  of  the  engine.  One  of  the  beauties  of 
the  automatic  adjustment  is  seen  in  A,  crank.  The  steam  pressure  steadily 
diminishes  from  the  time  of  impact,  and  the  steam  line  drops  nearly  ten 
pounds  ;  but,  compared  with  B,  it  carries  steam  very  much  longer,  endeavoring 
to  make  up  for  what  the  head  end,  A,  lacks.  The  race,  however,  was  a  stern 
chase,  and  it  was  impossible.  But  after  the  machine  shop  was  removed  from 
the  steam  chest,  B  B  shows  that  the  engine  was  in  excellent  adjustment,  one 
valve,  if  anything,  being  a  trifle  off  time,  but  the  steam  lines  are  so  nearly 
good  that  it  is  not  necessary  to  criticise  them. 

There  is  also  another  lesson  to  be  drawn  from  this,  viz. :  It  don't  pay  to 
joke  too  hard,  or  to  play  tricks,  one  workman  with  another,  in  a  job  like  this, 
where  one  man  may  forget  what  he  has  done,  or  another  one  forget  exactly 
where  he  left  off.  It  was  a  very  fortunate  occurrence  that  a  smash-up  did  not 
occur,  and  had  some  of  these  tools  passed  the  steam  passage  to  the  front  of 
the  steam  valve,  there  might  have  been  a  smash  with  serious  consequences. 
The  Indicator  only  tells  the  truth,  and,  if  the  steam  is  shut  away  from  the 
piston,  it  may  not  write  upon  the  Indicator  card  that  practical  joking  is 
expensive,  or  a  machine  shop  out  of  place  has  choked  the  steam  off,  but  it 
does  tell  distinctly  that  the  steam  don't  get  to  the  piston,  and  sensible  men, 
like  those  who  use  the  Indicator,  usually  commence  an  investigation  without 
waiting  for  a  smash.  There  was  never  a  better  illustration  of  the  real  value 
of  the  Incficator  than  this ;  and,  although  it  is  absurd  in  one  point  of  view,  we 
consider  the  instructive  as  predominant,  hence,  give  it  a  place  among  our  many 
lessons. 


TWENTY  YEARS    WITH  THE  INDICATOR.  115 


LESSON   XXXII. 


THE  point  in  the  following  needs  a  little  preface,  in  order  to  be  thoroughly 
digested  by  our  readers ;  we  mean,  of  course,  the  practical  ones.  Yet  it  is 
only  one  case  where  a  consulting  engineer  has  to  trample  down  both  ignorance 
and  prejudice,  and  can  only  let  daylight  shine,  where  prejudice  and  ignorance 
has  sway,  by  the  use  of  a  sledge  hammer.  The  point  in  question  is  one  which 
reaches  directly  the  pocket  of  the  victim  ;  and  for  this,  steam  users  are  not  so 
much  to  blame  as  those  men  who  sign  themselves  "  experts."  Briefly,  the 
case  is  as  follows  :  A  manufacturing  company  had  a  large  engine  and  boilers, 
and  a  first-class,  sensible,  clean,  and  intelligent  engineer.  The  engineer  had 
satisfied  himself  that  he  was  using  more  coal  than  he  should ;  precisely  the 
reason  he  did  not  know,  for  he  had  no  Indicator.  After  a  good  deal  of 
persuasion,  he  induced  the  manager  to  make  a  call  upon  us  for  advice.  We 
suggested  the  application  of  the  Indicator;  but  he  did  not  understand  the 
thing,  could  "  not  see  why  his  engineer  could  not  set  the  valves,"  and  repeated 
the  whole  train  of  arguments  which  are  so  often  rehearsed  to  the  man  who  is 
a  consulting  engineer,  and  has  any  practice.  He  finally  inquired  our  terms. 
"Fifty  dollars  a  day,"  we  answered  him,  "and  not  more  than  one  day  at  a 
time;  we  must  consult  our  other  work  and  appointments."  He  thought  that 
was  pretty  hard;  in  fact,  he  "would  not  pay  any  man  fifty  dollars  a  day,  —  it 
was  more  than  he  was  worth."  We  mildly  suggested  to  him  that  there  were 
other  men  who  could  apply  the  Indicator,  and  we  were  perfectly  willing  for 
them  to  have  every  chance.  But  in  his  case  it  was  not  sufficient  to  have  the 
Indicator  applied ;  but,  as  the  darkey  said  to  the  surgeon,  he  wanted  also  to 
apply  the  "  know  how,"  which  we  have  been  trying  to  learn  for  the  past  twenty 
years.  We  bade  him  good-bye,  and  good-naturedly  advised  him  to  call  again 
and  give  us  his  results.  A  few  weeks  after,  he  called,  bringing  some  Indicator 
cards,  and  frankly  confessed  that  while  the  engine  had  been  improved  some- 
what, he  was  thoroughly  terrified  at  the  amount  of  coal  it  was  running  through. 
He  presented  us  with  the  card  X  A  i,  Fig.  71,  and  any  one  who  knows 
anything  about  working  steam  would  not  dream  that  this  was  made  by  a 
Harris-Corliss  machine.  If  it  had  been  made  on  one  of  the  old-fashioned, 
grid-iron  cut-offs,  sliding  on  the  back  of  the  main  valve,  built  thirty  years  ago, 
we  would  have  called  it  a  pretty  fair  production  of  that  style  of  engine ;  but, 
as  to  its  comparison  with  any  modern  idea,  it  is  radically  deficient,  and  one  of 
the  worst  abortions  we  ever  saw  from  this  kind  of  an  engine.  The  old 
question  then  arose.  We  told  him  frankly  we  had  quite  enough  to  do  without 
the  job ;  at  the  same  time,  we  liked  just  such  a  job,  for  it  furnished  food  for 


u6 


TWENTY   YEARS    WITH   THE  INDICATOR. 


reflection  for  other  people  who  are  using  steam  power.  But  the  old  gentleman 
thought  the  price  was  abominable,  and  went  to  consult  his  treasurer.  A  few 
days  after,  he  and  his  treasurer  walked  in  with  the  same  diagrams.  A  half 
hour  was  spent  in  chatting  and  chaffing,  and  no  result  was  reached. 

In  about  a  week,  the  son  of  the 
agent  came  in,  bringing  the  cards 
which  our  expert  friend  had  taken, 
showing  the  state  in  which  the 
engine  was  left.  The  son  was  one 
of  those  intelligent  fellows,  who  not 
only  wants  to  know  what  is  going 
on,  but  also  some  good  reason 
why.  We  asked  him  if  he  had  any 
objection  to  our  running  our  Plani- 
meter  over  the  card.  "  Certainly 
not;  he  wanted  information."  In 
running  the  Planimeter  over  the 
card,  X  A  i,  we  told  him  that  he 
was  losing  about  25  per  cent,  of  his 
power  by  back  pressure;  in  other 
words,  that  the  back  pressure  was 
abominable;  that  the  engine  was 
largely  overloaded,  and  that  the 
draft  of  steam  did  not  allow  him  to 
realize  his  boiler  pressure;  but  that, 
if  he  could  afford  to  burn  five  tons 
of  coal  to  do  what  four  tons  ought 
to  do  much  better,  it  was  not  our 
business,  but  his.  We  finally  made 
him  a  proposition,  that  we  would 
indicate  the  engine,  adjust  the 
valves  to  suit  ourselves,  and  be 
responsible  for  results,  if  he  would 
agree  that  the  engine  should  be  let 
alone,  and  we  would  take  one-half 
FlG- 7I-  of  what  we  could  save  in  fuel  for 

thirty  days'  running  time ;  to  take  his  last  four  or  six  months'  account,  and 
average  the  time,  and  take  our  thirty  days'  run,  actual  weight,  and  let  himself, 
his  father,  and  his  engineer,  make  their  own  figures.  He  went  away.  A  day 
or  two  after,  he  accepted  our  proposition.  We  named  a  day,  and  obtained  a 
half  dozen  reproductions  of  X  A  i ,  with  little  variations,  according  to  the 
load.  The  engine  is  23  X  60  inches,  57^  revolutions,  90  pounds  of  steam, 
scale  40.  Measuring  from  the  atmospheric  line,  or  line  of  rest  on  the  instru- 


TWENTY   YEARS    WITH   THE  JXDICATOR. 


117 


merit,  we  get  85  pounds  into  the  cylinder.     It  is  hard  work  to  tell  where  the 

cut  off  is,  or  where  the  expansion  line  commences.     There  is  evidently  no 

difficulty  in  telling  where  it  ends,   pr  that  there  is  a  slight  amount  of  back 

pressure   in    the   cylinder.     At   the   commencement    of    the  exhaust,  with   a 

nine-inch  exhaust  pipe   wide   open 

into  the  air,  and  not  more  than  40 

feet  long  at  that,  at  A,  we  get  25^ 

pounds  back  pressure  ;  at  the  centre 

of  the  stroke,  we  get  7^2   pounds, 

and  at  B,  we  have  5  pounds  left. 

The  engine  was  burning  twelve  and 

a  half  tons  of  coal  a  day,  of  eleven 

hours,  developing  750  horse-power, 

of  which  595  horse-power  was  trans- 

mitted, less  156  horse-power   back 

pressure.     If  our  feaders  will  figure 

this  a  little,  they  will  find  that  the 

engine    was     running    with    three 

pounds  of  Lehigh  furnace  coal,  or 

what  may   be   better   known,   per- 

haps, as  "  broken,"  in  pieces  about 

the  size  of  a  man's  fist.     Slightly 

over  25  per  cent,  of  the  load  was 

thrown   away.       After  four   hours' 

work,  a  part  of  which  was  spent  in 

making  explanations,    and    several 

stoppages,    we    produced   X  A  2, 

which  represents  470  horse-power, 

nearly,    and    yet   was    driving    the 

same  machinery  as  X  A  i. 

It  will  be  seen  that  X  A  2  has 
exactly  90  pounds  of  steam  in  the 
cylinder  at  the  impact;  that  the 
point  of  cut  off  is  very  sharply 
defined  ;  that  the  steam  pressure,  to 
the  extent  of  five  pounds,  is  lost  . 

.  , 

so  that  we  start  with  90  pounds,  and 
cut  off  very  sharply  with  85  pounds.  The  expansion  line,  without  applying 
the  theoretical  curve,  to  the  practiced  eye,  is  a  beauty.  It  must  be  remem- 
bered that  every  pound  of  the  mean  pressure  on  the  piston  of  this  engine 
gives  7.239  horse-power  ;  hence,  37><  per  cent,  of  the  load  by  X  A  i  is  exactly 
thrown  away.  Yet  no  heating  was  being  done  ;  the  engine  was  exhausting  in 
both  cases  into  the  open  air.  X  A  2  shows  iV2  pounds  of  back  pressure  on 


n8  TWENTY  YEARS    WITH  THE  INDICATOR. 

an  average,  commencing  slightly  in  excess  of  that,  and  terminating  the  exhaust 
by  a  very  handsome  compression,  and  almost  absolutely  correct  admission. 

This  is  a  most  interesting  case,  because  it  is  based  on  absolute  facts.  At 
the  end  of  three  weeks  from  the  adjustment  of  the  valves,  the  old  gentleman 
called  to  see  what  our  charge  was  to  be.  We  referred  him  to  the  engagement 
made  in  his  son's  letter.  A  day  or  two  afterward,  the  treasurer  called  with 
the  same  question.  We  simply  referred  to  our  agreement,  which  was  in 
writing.  The  day  before  the  termination  of  the  thirty  working  days,  the  son 
called,  asking  us  if  we  expected  a  saving  which  would  amount  to  30  tons  of 
coal.  We  told  him  we  expected  a  saving  of  over  70  tons  of  coal,  as  the  total 
amount  saved,  and  he  told  us  they  were  going  to  exceed  that  amount,  he 
thought.  Here  the  matter  was  left  until  the  thirty  days  terminated.  The 
account  rendered,  is  as  follows:  For  four  months'  working  days,  24,783 
pounds  of  fuel  were  used,  including  banking  fires  at  night,  and  on  Sunday, 
under  boilers  sufficient  to  run  their  big  fire  pump.  For  the  thirty  days  after 
the  readjustment,  5,140  pounds  of  coal  were  saved  each  day,  the  fuel  account 
being  charged  with  banking  the  fires,  and  maintaining  a  steam  pressure  not 
less  than  50  pounds  on  four  boilers  every  Sunday  for  the  big  fire  pump.  The 
coal  in  the  coal-house  cost  $6.40  per  ton,  making  a  clean  saving  of  $16  per 
day,  saying  nothing  of  the  few  pounds  of  coal  over  2^  tons.  They  figured, 
therefore,  the  saving,  by  the  simple  readjustment  of  the  valves,  to  be  $480  for 
five  weeks'  running  time,  66  hours  per  week,  making  thirty  working  days. 
The  letter  received  from  the  old  gentleman  a  few  days  after,  enclosing  his 
check,  stated  simply  as  follows :  "  Six  weeks  ago  I  would  not  have  believed 
that  you  or  any  other  man  could  have  shown  how  ignorant  a  man  can  be  in 
the  use  of  fuel.  The  only  thing  I  regret  is  that  I  had  not  long  ago  employed 
you.  If  this  should  ever  be  given  in  the  columns  of  your  paper,  do  not  give 
any  clew  to  the  mill  or  the  manager,  if  you  have  any  respect  for  yours  truly." 

And  yet  this  is  not  as  bad  as  some  mills  are  actually  doing  today.  The 
way  out  is  simple,  and  some  of  our  corporations,  that  consider  an  engineer  is 
getting  above  his  business  when  he  attempts  to  learn  something,  may  perhaps 
get  down  1  j  their  business  through  their  legitimate  representatives,  if  they 
themselves  were  to  learn  more  of  the  Indicator,  of  the  absolute  facts  which  it 
records,  and  of  the  saving  which  the  proper  reading  of  the  simple  pencil  lines 
of  the  instrument  upon  a  piece  of  paper  will  allow  a  man  practiced  in  it  to 
effect.  Dollars  and  cents  are  the  measure  of  most  men's  success,  and  they  are 
quite  as  ignorant  why  a  man  should  spend  years  in  this  practice,  and  then  ask 
them  but  a  very  nominal  sum  indeed  for  the  use  of  his  experience,  as  the  old 
darkey  was  why  the  surgeon  should  charge  $25  for  fifteen  minutes'  work,  which 
might  save  a  man's  life,  not  taking  into  account  the  years  he  had  devoted  to 
study  in  acquiring  an  intimate  knowledge  of  human  anatomy.  But  there  are 
people  who  can  only  learn  from  experience,  and  the  case  which  we  give  here  is 
peculiarly  one  of  these  applications. 


TWENTY  YEARS    WITH  THE  INDICATOR. 


119 


LESSON   XXXIII. 


THE  diagrams,  Fig.  73,  which  are  the  subject  oi  this  lesson,  came  from  a 
Reynolds-Corliss,  24  inches  in  diameter,  48  inches  stroke,  rated  at  330  horse- 
power, making  76  revolutions  per  minute,  40  scale  (boiler  pressure  not  given), 
driving  a  cotton  mill  in  Mississippi.  This  inquiry  comes  with  them :  "  What  do 
you  think  of  them,  and  what 
improvements  would  you  sug- 
gest which  will  work  for  our 
advantage?  " 

Apparently  there  would 
appear  to  be  little  difference, 
and  yet  the  crank  end,  while 
seeming  to  cut  off  the  shortest, 
is  doing  more  work  than  the 
head  end.  The  cut  off  is 
cleanest  on  the  head  end ;  but, 
after  the  valve  is  closed  on  the 
crank,  the  steam  seems  to  come 
through  under  the  valve,  and 
the  expansion  line  is  higher 
than  it  should  be.  Remedying 
this  would  be  an  improvement 
which  would  save  money  to  the 
concern.  The  head  end,  if  at- 
tention is  given  to  the  vertica 
line,  will  be  found  late  in  taking 
steam.  We  would  quicken  that 
valve  slightly,  by  opening  it  a 
trifle  sooner.  This  would  have 
a  tendency  to  somewhat  in- 
crease the  pressure,  which 
would  probably  go  nearer  to 
the  dotted  line  on  that  end. 
On  the  diagram  marked  C, 
the  steam  line  proper  is  very 
short,  while  the  cut  off  is 
apparently  at  B.  This  valve,  seemingly,  opens  quicker  than  the  other,  and,  if 
the  instrument  is  correct,  the  line  leans  the  wrong  way,  as  it  leans  to  the 
vertical  line  rather  than  from  it  If  the  valve  was  opened  slieMv 


FIG.  73. 


120  TWENTY  YEARS    WITH  THE  INDICATOR. 

and  the  cut-off  then  adjusted  to  do  the  same  amount  of  work  upon  each 
end,  there  is  little  doubt  but  there  would  be  less  loss  in  pressure  than  is  shown 
by  the  diagram.  Taken  all  in  all,  the  diagrams  are  very  good,  yet  the  engine 
could  be  made  to  do  its  work  with  a  perceptibly  less  amount  of  fuel  by  the 
changes  we  have  indicated,  and,  if  they  are  made,  we  should  be  glad  to  see 
other  diagrams  after  the  alteration. 

At  A,  on  each  of  the  diagrams,  it  will  be  seen  that  the  commencement  of 
the  exhaust  is  abrupt,  and  the  toe  of  the  diagrams  is  square  on  the  wrong  side. 
If  the  movement  of  the  exhaust  valves  was  slightly  quickened,  the  dotted  line, 
D,  would  be  produced  upon  that  end,  while  E  would  be  produced  on  the 
termination  of  the  expansion  line,  and  the  commencement  of  the  exhaust  at  F. 
Both  these  outlines  will  be  produced  by  shortening  the  jim -cranks  slightly,  if 
it  is  the  ordinary  Reynolds-Corliss  engine.  The  boiler  pressure  in  this  case  is 
not  given;  had  it  been,  we  might  have  told  whether  further  improvements 
could  have  been  made.  It  is  evidently  plus  one  hundred  pounds,  as  nearly 
one  hundred  pounds  is  realized  in  the  cylinder.  On  the  whole,  it  is  better 
work  than  the  average,  and  speaks  well  both  for  the  builder  of  the  engine  and 
those  who  have  it  in  charge. 


LESSON   XXXIV. 


IN  this  lesson  we  have  a  veritable  study,  not  exactly  in  natural  history, 
but  in  the  misuse  of  steam.  These  diagrams,  Fig.  74,  were  taken  from  a 
Greene  engine,  and  a  machine  capable  of  doing  much  better  work  than  this. 
The 'man  in  charge  of  this  engine  had  an  Indicator,  but  whether  he  did  not 
know  how  to  use  it,  or  did  not  want  to,  we  cannot  tell.  The  diagrams  are 
about  as  bad  as  anything  can  well  be.  C  D  represents  vertical  lines,  showing 
the  boiler  pressure,  55  pounds,  40  scale.  If  we  take  A,  and  start  on  the 
admission  line,  we  find  the  admission  line  leaning  away  from  the  vertical,  and 
this  tells  us  conclusively  that  the  motion  of  the  valves  is  late.  The  steam  rises 
to  i,  where  a  sharp  off-set  is  made,  as  the  piston  begins  to  move  at  that  point. 
The  pressure  then  rises  to  2,  where  another  off-set  is  made,  and  very  much 
more  rapid  than  the  other.  This  is  owing  to  the  accelerated  motion  of  the 
piston.  The  motion  of  the  piston  is  increasing  in  speed  all  this  time;  the 
motion  of  the  valve  is  also  late  in  its  opening,  and  so  does  not  keep  up  with 


TWENTY   YEARS    WITH   THE  INDICATOR.  121 

that  of  the  piston.  The  motion  of  the  piston  from  i  to  2  is  much  slower  than 
from  2  to  3,  hence  the  admission  line  varies  less  from  the  perpendicular  from  I 
to  2  than  from  2  to  3.  At  3,  fifty  pounds  pressure  is  utilized,  and  from  3  to  4 
we  may  call  it  a  steam  line.  At  4  the  valve  is  closed.  The  expansion  line 
continues  to  5,  where  the  exhaust  valve  partially  opens.  The  expansion  line 
then  commences,  and  returns  on  the  exhaust  line,  until  we  meet  a  very  queer 
character  near  6.  What  makes  this  peculiar  notch  at  that  end  of  the  diagram, 
and  in  that  way,  we  confess  we  are  unable  to  explain  satisfactorily.  If  the 
engines  had  grid-iron  valves  for  exhaust,  the  valves  might  have  closed  and 
traveled  past  the  opening  again,  so  as  to  compress  the  steam  to  a  point  and 
then  reduce  it  again  by  admitting  it  into  the  exhaust  until  the  valve  traveled  to 
another  grid. 

B  is,  in  a  general  way,  worse  than  A.  The  exhaust  valve  closes  at  7, 
making  a  very  peculiar  kink.  Compression  taking  place,  the  pencil  of  the 
Indicator  travels  past  8,  drops  down  when  the  piston  of  the  engine  begins  to 


FIG.  74. 

move,  and  begins  to  travel  backward,  passing  at  8,  running  up  to  9,  at  which 
point  the  piston  starts  on  its  journey,  the  valve  opening  very  late ;  at  10  it  is 
still  later,  and  at  1 1  very  late.  The  round  outline  of  A  shows  that  the  valve 
does  not  supply  steam  in  any  quantity  sufficient  for  the  area  exposed.  From 
ii  to  12  we  may  call  it  a  steam  line.  From  12  on,  the  expansion  line  takes 
place,  making  one  of  the  most  outrageous  cards  found  in  practice.  We  do 
not  know  of  any  explanation  for  this  appearance  unless,  perhaps,  the  engineer 
never  knew  the  use  of  the  Indicator,  possibly  did  not  care  to  know,  or  else 
that,  in  attempting  to  change  the  valves  by  the  Indicator,  he  had  got  lost,  and 
this  is  probably  the  nearest  to  a  plausible  explanation  we  can  suggest. 

If  we  were  to  study  this  card  for  economy,  we  find  that  A  figures  240,  B 
190,  or  in  that  proportion.  Little  more  than  half  the  steam,  will  do  the  work  of 
A,  and  considerable  less  than  one-half  the  steam  used  at  B,  if  properly  applied. 
Here,  then,  we  have  an  engine  doing  its  work  nearly  thirty  per  cent,  more  at 
one  end  than  at  the  other,  and  using  fully  double  the  steam  that  it  should  to 
accomplish  the  work. 


122  TWENTY  YEARS    WITH  THE  INDICATOR. 

Some  parties  sometimes  ask  questions  in  reference  to  compression.  They 
do  not  understand  how  the  lines  7,  8,  9,  10  are  made.  Remember  that  the  pencil 
of  the  Indicator  travels  up  and  down  while  the  motion  of  the  paper  cylinder  is 
at  right  angles  with  the  pencil,  or,  we  might  say,  is  backward  and  forward,  just 
like  the  piston  of  the  engine.  At  figure  7  the  exhaust  valve  closes  over  the 
exhaust  port ;  the  piston  has  not  reached  the  end  of  its  stroke  proportionately, 
as  the  distance  from  7  to  the  vertical  line  is  to  the  whole  length,  C  D.  What- 
ever steam  is  in  the  cylinder  at  the  time  is  closed  in.  Now,  as  the  piston 
approaches  the  line,  D,  the  steam  in  the  cylinder  is  compressed  to  a  greater 
density.  This  compression  raises  the  pencil  of  the  instrument  slowly,  making 
the  rounded  outline  in  this  case  instead  of  an  angular  one.  When  the  piston 
gets  as  far  back  as  8,  for  some  reason,  perhaps  leaky  rings  or  valves,  or 
condensation  of  steam,  the  pressure  gradually  diminishes,  and,  instead  of 
holding  the  Indicator  piston  up  as  high  as  8,  the  change  which  takes  place  in 
the  steam  reduces  the  pressure,  and  the  piston  of  the  Indicator  falls  downward ; 
it  reaches  the  lowest  point,  as  will  be  seen,  at  the  very  extreme  end  of  the 
travel  of  the  piston.  The  steam  valve  now  commences  to  open,  and  steam  is 
let  slowly  into  the  cylinder.  The  piston  commences  to  go  back  on  its  outward 
stroke,  and  the  steam  increases  in  pressure,  making  the  line  up  to  the  figure  9. 
During  the  time  this  line  is  being  made  the  speed  of  the  piston  is  very  slow 
indeed,  and  it  is  just  passing  off  the  dead  center.  As  the  piston  starts  away  it 
gradually  grows  faster  and  faster  every  inch  that  it  travels,  so  that  when  the 
Indicator  piston  reaches  9,  the  piston  of  the  engine  has  started  to  travel  much 
faster,  and  the  line  falls  back  from  the  vertical  line,  D,  much  more  between  9 
and  10  than  between  8  and  9,  and  the  same  applies  to  10  and  n  as  greater 
than  9  and  10.  If  the  motion  of  the  steam  valve  is  late  at  the  commencement 
it  does  not  open  any  faster,  for  it  has  no  connection  with  the  piston,  and  the 
volume  of  the  cylinder  increases  very  rapidly.  Steam  should  be  admitted  to 
the  cylinder  by  opening  the  valves  when  the  piston  is  on  its  dead  center,  or 
actual  point  of  rest,  if  possible.  This  can  be  done  without  giving  any  shock 
to  the  engine,  or  without  any  danger.  Evidently  whoever  had  been  working 
with  this  engine  was  either  ignorant  or  careless.  It  would  require  an  hour, 
perhaps,  to  put  it  in  first-rate  order,  and,  with  an  engine  not  having  large  areas 
of  port  and  valve — and  the  Greene  engine  is  noted  for  this  —  the  results  would 
have  been  far  less  economical,  if,  indeed,  there  is  any  economy  in  the  diagrams 
at  all. 

The  first  thing  to  do  in  a  job  of  this  kind,  in  adjusting,  would  be  to  throw 
the  eccentric  ahead  two  or  three  inches  on  the  shaft,  quickening  all  the  motions. 
Then  it  is  a  question  of  give  and  take ;  perhaps  one  motion  would  have  to  be 
slowed,  and  another  one  quickened  a  little.  In  a  future  volume  in  this  series, 
we  purpose  to  take  up  this  subject  of  making  the  alterations  in  an  engine,  and 
give  the  whole  series  of  diagrams,  in  order  to  show  just  what  is  done  by 
making  a  little  change.  We  would  not  advise  our  readers,  however,  to  imitate 


TWENTY  YEARS   WITH  THE  INDICATOR. 


123 


the  diagrams  given  in  this  lesson,  upon  any  account,  for  they  are  worse  than 
bad,  if  it  is  possible  to  have  them  so.  A  good  engineer  would  not  make  such 
•i  diagram  if  he  had  an  Indicator,  and  knew  what  it  was  for.  If  this  engine 
was  doing  200  horse-power,  and  coal  was  worth  $4  a  ton,  the  proper  arrange- 
ment of  the  valves  by  the  Indicator  would  save  just  about  half  the  coal,  to  say 
nothing  of  more  regular  speed  and  less  keying  up  of  the  engine. 


LESSON  XXXV. 


THE  diagrams  in  this  lesson  were  taken  from  the  report  of  Henry  Hiller, 
the  Chief  Engineer  of  the  National  Boiler  Insurance  Company,  of  Manchester, 
England,  for  1881.  It  is  not  an  uncommon  occurrence,  and,  at  the  same  time, 
it  is  very  peculiar.  The  cylinder  is  16  inches  in  diameter;  stroke  36  inches; 
revolutions  per  minute  65;  scale  No.  i,  22  per  inch;  boiler  pressure  57 
pounds.  No.  2,  same  diameter,  stroke,  and  revolutions  as  the  previous  one; 
scale  12.  These  diagrams  were  taken,  No.  i  from  one  cylinder,  and  No.  2 
from  the  other  cylinder  of  a  pair  working  together. 


l.H.P. 


3.36 


ATMOSPHERIC  LINE 


FIG.  75. 

Mr.  Hiller  remarks  as  follows :  "  One  of  them  was  actually  doing  no 
work,  but  was  -really  being  driven  by  the  other.  One  of  the  engines  they 
stopped  at  our  suggestion,  and  the  water  consumption,  as  shown  by  the 
diagrams,  reduced  from  66  pounds  to  35.4  pounds  per  indicated  horse-power 
per  hour  " 


I24 


TWENTY  YEARS    WITH  THE  INDICATOR. 


These  diagrams  are  peculiar  in  more  respects  than  one.  No.  i  is  very 
late  in  taking  steam  at  both  ends,  more  so  at  one  end  than  the  other.  What- 
ever the  pattern  of  the  engine  may  be,  no  description  being  given,  the  steam 
would  seem  to  be  badly  wire-drawn.  The  expansion  line  is  a  wicked  one,  and 
the  effective  pressure  differs  radically  between  the  two  ends.  Sixty-six  pounds 
of  water  per  hour  is  an  outrageous  quantity.  Twenty-five  or  six  is  accom- 
plished on  old-fashioned  slide  valve  engines,  and  as  low  as  thirteen  to  sixteen 
by  the  Corliss  condensing. 

Diagram  No.  2  is  more  than  peculiar.  The  steam  is  admitted,  cut  off 
sharply,  and  expanded  across  the  atmospheric  line  at  about  one-fifth  stroke. 
That  part  of  the  diagram  which  is  below  the  atmospheric  line,  in  which  the 


H.P.  =    —  2.5 


IjMOSpHERtC  LING. 


FIG.  76. 

steam  is  long  drawn  out  beyond  its  usefulness,  has  an  area  larger  than  that  of 
the  pressure  on  the  piston  above  the  atmospheric  line,  and  it  is  the  same  at 
both  ends,  although  a  little  more  difference  exists  in  one  than  in  the  other. 
No  doubt  some  of  our  readers  will  get  bothered  in  measuring  this  with  the 
Planimeter.  They  are  reproduced  full  size,  so  that  they  may  be  measured. 
The  boiler  pressure,  in  this  case,  is  57  pounds,  while  the  realized  steam 
pressure  is  only  24  or  24^  pounds.  The  indicated  horse-power  of  this  pair 
of  cards  is  less  than  nothing;  in  other  words,  the  horse-power  is  minus  2}^, 
or,  to  put  it  into  still  another  shape,  2^  horse-power  is  being  developed 
against  the  other  engine.  This  is  caused  by  the  expansion  of  the  steam,  which 
is  drawn  out  past  its  useful  or  efficient  force,  so  that  it  really  retards,  or  would 
retard,  the  action  of  the  engine,  were  it  not  that  the  other  side  is  driving  so 
much  more  power,  and  this  is  doing  very  wastefully  what  it  is  doing  at  ail, 


TWENTY  YEARS    WITH  THE  INDICATOR.  125 

from  the  fact  of  the  steam  being  admitted  at  a  much  lower  pressure  than  in 
the  boiler,  and  then  being  expanded  at  such  a  ratio  that  it  practically  ceases  to 
be  of  any  use.  We  do  not  wonder  that,  when  this  engine,  as  Mr.  Hiller 
advised,  was  stopped,  the  other  engine  did  all  the  work  with  less  fuel.  The 
measurement  of  the  spaces,  below  the  atmospheric  line,  is  always  taken  from 
the  measurement  of  that  space  above  the  atmospheric  line,  by  the  action  of  the 
Planimeter ;  but  in  this  case  the  space  below  the  line  is  of  the  most  account, 
consequently  the  Planimeter  gives  us  a  negative  result  at  the  end  of  its  travel. 
This  will  be  an  excellent  exercise  for  learners  to  practice  upon,  and  it  will  give 
them  useful  information  in  regard  to  taking  the  areas  of  surfaces  which  are 
somewhat  mixed. 

If  we  take  No.  i,  in  this  illustration,  we  have  the  fact  of  38  pounds  of 
steam,  out  of  57  boiler  pressure,  being  shot  through  the  ports  on  to  the  piston 
head,  after  it  has  been  on  its  way  some  time,  so  that  it  never  catches  up.  We 
then  have  a  low  ratio  of  expansion,  from  the  fact  of  wire-drawing  and 
throttling,  and  the  steam  is  reduced  in  pressure  to  that  extent  which  makes  it 
a  most  exorbitant  consumer  of  water. 

In  No.  2,  the  same  thing  is  carried  out.  The  steam  is  put  into  the 
cylinder  of  the  engine  to  do  less  than  any  work  at  all,  and,  aside  from  wasting 
ihe  amount  of  steam  which  is  put  into  the  cylinder,  the  parties  were  also 
wasting  power  which  had  to  be  made  up  by  the  other  cylinder  of  the 
machine.  This  is  a  most  unique  example.  It  is  different  from  anything  which 
we  have  before  had,  and  does  not  show  very  good  economy  in  the  use  of 
steam.  We  have  introduced  it  in  this  place  more  for  the  purpose  of  giving 
our  readers  practice  with  their  Planimeters  and  computations,  than  because  of 
anything  which  is  radically  instructive.  In  No.  2,  the  dotted  line  produces 
eight  pounds  of  vacuum,  or  pull-back,  while  the  other  end  only  produces  five 
pounds  at  the  starting  point.  The  space  of  the  stroke  traveled  by  drawing  the 
ste?m,  below  the  atmospheric  line,  is  double,  or  more  than  the  space  traveled 
by  the  piston  before  the  expansion  line  crosses  the  atmospheric  line ;  but  where 
the  space  is  laid  out  different,  the  Planimeter  gives  us  a  reading  that  both  sides 
are  negative,  results.  The  valves  of  engine  No.  2  must  have  been  in  elegant 
order,  for  they  make  first-class  air-pumps,  or  would,  if  they  had  water  with 
which  to  condense  the  steam,  and  from  which  to  extract  the  air.  Taken  all  in 
all,  these  cards  are  a  very  interesting  study,  and  only  show  what  can  be 
done,  if  parties  would  only  try ;  but  we  should  much  rather  that  they  would 
try  on  some  other  man's  coal  pile  than  our  own.  Perhaps  some  of  our  readers 
will  gather  ideas  from  this  that  will  set  them  to  thinking  more  closely,  and  if 
they  will  attempt  to  erect  the  theoretical  curve  upon  either  one  of  the  diagrams 
they  will  find  that  all  new  rules  will  give  them  a  great  deal  of  variance. 


126  TWENTY  YEARS    WITH  THE  INDICATOR. 


LESSON  XXXVI. 

THE  diagrams  shown  in  this  lesson  are  from  a  Wheelock  engine,  14^  X 
4^mches,  76  revolutions,  boiler  pressure  72  pounds,  scale  30.     The  diagrams 

are  simultaneous,  or  taken  at  the  same 
instant  of  time;    A  the  crank,  B  the 
head  end.     The  boiler  pressure,  in  this 
case,  is  72  pounds;    the  Indicator  ac- 
counts for  only  60  pounds  upon  the 
head  of  the  piston,  or  one-sixth  the 
boiler  pressure  does  not  enter  the  cyl- 
inder.   We  know  nothing  of  the  reason. 
The  crank  card,  in  this  case,  has  rather 
a   neat  outline,   but   there  are  radical 
faults  in  it.     We  find  the  line  from  A 
to  C,  instead  of  becoming  concave,  or 
expanding,   as   steam    should   do,   be- 
comes convex.     The  dotted  line  shows 
about  what  should  occur.     The  cut  off 
of  this  diagram  is  clearly  marked  at  A  ; 
there  need  be  no  guessing  at  it.     The 
clearance  of  the  engine  is  not  given, 
hence  we  have  nothing  in  particular  to 
assume.     If  we  take  the  steam   as  it 
probably   cut   off  at   A,   the  pressure 
should  immediately  drop  to  the  dotted 
line,   and    follow  it,   or  very  near  it, 
instead   of  which   we  find   that  steam 
actually  enters  after  the  valve  is  closed 
at    A,    or    is    maintained    somewhere 
between  the  cut-off  valve  and  the  pis- 
ton head.     This  steam  either  leaks  in, 
or   has    been   fed   in,   we  cannot    say 
which,  and   the  dotted   line  gives  the 
appearance    of   the   first    part   of   the 
hyperbolic   curve,   which    is    concave, 

while  the  actual  line  ol  the  instrument  is  convex.     The  line,  as  erected,  should 
be  much  better. 


TWENTY  YEARS    WITH  THE  INDICATOR. 


727 


Diagram  B  is  one  of  those  peculiar  features  that  \ve  sometimes  come 
across,  and  is  correctly  stated  as  being  a  minus  quantity ;  in  other  words,  B 
does  less  than  nothing,  but  rather  holds  back  on  A  somewhat,  and  A  not  only 
has  to  do  all  the  work  the  engine 
is  doing,  but  has  to  help  do  what 
B  holds  back.  These  diagrams 
are  both  of  full  size,  and  exact 
reproductions  from  the  ,  original 
cards ;  therefore,  our  readers  can 
measure  them,  or  run  their  Plani- 
meters  over  them.  It  would  be 
interesting  for  them,  especially 
upon  B,  to  see  exactly  where  the 
difference  lies.  The  diagram,  B, 
shows  some  of  the  same  features 
that  A  does,  and,  while  it  is  a 
negative  quantity,  shows  plainly 
the  feeding  of  the  steam  into  the 
cylinder  after  the  valve  had  closed. 
The  precise  reason  for  this  we 
cannot  say  —  probably  a  leak. 
The  expansion  lines  on  these 
cards  are  not  perfect,  and.  not 
having  the  clearance,  we  cannot 
lay  out  exactly  what  it  should  be. 
It  is  a  self-evident  fact  that  an  ad- 
justment of  the  valves  would  be 
very  advantageous  to  parties  run- 
ning the  engine.  We  cannot 
guess  at  dimensions  or  conditions 
under  which  an  engine  is  working, 
and  no  man  who  is  honest  with 
himself  can  apply  exact  measure- 
ments or  give  the  precise  data 
that  shall  lead  to  a  computation 
of  the  efficient  work  of  such  an  FlG-  78> 

engine.  The  diagrams  are  peculiar;  they  are  not  uncommon,— not  especially 
as  regards  this  engine,  — but  diagrams  even  worse  than  this  are  much  nearer 
general  practice.  If  the  cut  off  on  the  head  end  is  lengthened  and  the  crank 
end  shortened,  to  even  up  the  load,  the  head  end  will  be  doing  something,  and 
the  crank  end  will  not  have  to  do  all  the  load  and  a  little  more.  These 
diagrams  will  bear  study,  analysis,  and  computation. 


128  TWENTY  YEARS    WITH  THE  INDICATOR. 


LESSON   XXXVII. 


THE  diagram  in  this  lesson  will  be  lull  of  interest  to  many  of  our  readers 
who  have  been  following  the  lessons  closely,  and  have  familiarized  themselves 
somewhat  with  the  arguments  usually  advanced.  It  is  from  the  so-called  high- 
speed engine,  18  X  36  inches,  running  92  revolutions  with  90  pounds  of  steam, 

and  was  sent  to  us  by  the 
owner  of  the  engine,  asking 
if  we  would  tell  him  what 
were  the  defects,  and  what 
the  percentages  of  useful  ef- 
fect. The  defects  are  of  the 
class  usually  found  in  en- 
gines where  people  build 
them  without  taking  advan- 
tage of  knowledge  gained 
by  experience  and  practice. 
The  line,  A  B,  is  the  vacuum 
line ;  A  C,  the  line  of  boiler 
pressure,  as  well  as  the  boun- 
dary of  the  clearance ;  C  D 
is  the  boiler  pressure ;  E  F  is 
the  realized  pressure  in  the 
cylinder;  F  G  the  line  of 
cylinder  pressure;  H  I  is 
the  theoretical  curve  erected 
from  the  point  of  actual  cut 
off,  or  the  time  the  valve 
really  closes  in  its  stroke. 
The  distance  between  the 
lines,  A  C  and  E  F,  desig- 
nated by  the  letter  M,  is  the 
clearance  of  the  engine  from 
actual  computation,  and  is 
F1G'  79'  enormous.  We  have  here  a 

rather  curious  specimen  of  diagram.  The  compression  is  very  large,  as  it 
commences  before  the  piston  on  its  return  stroke  reaches  K.  After  the 
compression  is  finished,  the  motion  of  the  steam  valve  is  somewhat  late,  and 
the  jog,  or  notch,  near  the  letter  F,  shows  that  steam  is  not  promptly  admitt 


TWENTY  YEARS    WITH  THE  INDICATOR.  129 

•  * 
in  full  volume.     It   almost   immediately  falls   off  again,   and   the   difference 

between  the  perceptible  closing  of  the  valve,  and  the  real  closing  of  the  valve, 
amounts  to  more  than  two  inches,  and  the  maximum  amount  of  steam 
admitted  into  the  cylinder  is  69  pounds.  But  this  is  not  the  worst  feature. 
After  the  cut-off  valve  closes  there  would  seem  to  be,  between  the  valve  and 
the  piston,  a  large  amount  of  steam,  or  else  the  valve  is  leaking  badly.  This 
will  be  found  by  the  expansion  line  which,  at  I,  is  6  pounds  above  the  line  of 
theoretical  expansion.  This  engine  does  not  approximate  good  practice 
anywhere,  and  even  in  the  exhaust,  which  is  through  only  40  feet  of  pipe  into 
the  open  air,  it  will  be  found  that  there  are  3^  to  6  pounds  of  back  pressure. 
Among  other  inquiries  was,  "What  is  the  percentage  of  useful  effect?"  In 
erecting  the  theoretical  curve,  we  have  given  the  engine  all  the  benefit  of  the 
doubt,  and  have  placed  the  point  of  cut  off  at  H,  on  the  line,  F  G,  which  is  as 
nearly  as  possible  to  the  absolute  point  of  cut  off.  We  have  here  69  pounds 
of  steam  cut  off  at  -f^-  of  the  stroke.  The  Indicator  lines  give  us,  by  the 
Planimeter,  2.48,  while  the  theoretical  curve,  with  the  direct  point  of  cut  off, 
gives  us  2.22,  giving  us  ten  per  cent,  leakage  of  the  valve,  and  ten  per  cent,  of 
the  total  amount  of  steam  used  is  sifted  through  the  valve  after  it  is  closed. 
Now  we  use  69  pounds  of  steam  in  the  cylinder,  by  the  Indicator.  We  had 
90  pounds  in  the  boiler  and  89  pounds  in  the  steam  chest.  Giving  the  engine 
the  benefit  of  good  practice,  and  calling  for  only  95  per  cent,  of  the  boiler 
pressure  in  the  cylinder,  we  should  have  85^  pounds  by  the  Indicator,  instead 
of  69 ;  therefore,  the  effective  value  of  the  engine  is  80  per  cent,  of  boiler 
pressure.  The  engine  cuts  off  at  -f^-  of  the  stroke.  If  the  full  boiler  pressure, 
was  used,  or,  say  95  per  cent,  of  it,  as  is  the  case  with  all  good  engines,  instead 
of  cutting  off  at  -fg?  it  would  cut  off  at  T2^°7  of  the  stroke.  This  is  further 
proved  by  the  fact  that  the  track  of  the  Indicator,  on  the  diagram  gives,  by 
the  Planimeter,  2.48,  the  theoretical  curve  2.22,  and  cutting  off  at  -j^-,  2.38, 
with  the  Planimeter,  allowing  the  same  fault  of  compression  and  back  pressure 
which  now  exists.  Hence,  if  we  could  get  the  full  boiler  pressure,  85^ 
pounds,  into  the  cylinders,  we  should  save  27^  per  cent,  of  the  steam  at 
each  end  of  each  stroke,  or  over  one-quarter  of  all  the  steam  used,  by  this 
simple  saving  alone.  This  grade  of  expansion  would,  no  doubt,  yield  higher 
than  27-j1Q-  per  cent.,  from  the  fact  of  there  being  more  loss  by  wire-drawing 
of  the  steam  to  69  pounds  than  there  would  be  by  doing  the  same  load  by  the 
full  boiler  pressure,  85}^  pounds.  Therefore,  to  answer  the  question  which  is 
asked  us,  "  What  is  the  effective  value  of  this  engine  ?  "  —  it  is  lessened  20  per 
cent,  in  boiler  pressure,  1 2  per  cent,  by  leakage  of  the  valve,  and  27  per  cent, 
in  the  amount  of  steam  used,  if  it  could  do  the  work  at  95  per  cent,  of  the 
boiler  pressure ;  and  the  actual  value  of  the  engine,  as  an  actual  transmitter 
of  power  or  consumer  of  steam,  is  less  than  50  per  cent,  that  of  a  first-class, 
modern-built  engine,  working  upon  principles  which  are  every  day  practiced 
in  New  England  by  the  best  builders.  In  all  this  computation  we  take  the 


130  TWENTY  YEARS    WITH  THE  INDICATOR. 

steam  in  the  boiler  at  one  hundred  per  cent.  This  is  no  doubt  a  general 
arrangement,  and  those  parties  who  have  little  or  no  faith  in  the  Indicator  can 
submit  this  to  any  engine  builder  who  has  any  reputation  for  first-class  work, 
and  they  will  find  it  precisely  as  we  state.  The  line,  K,  shows  the  volume  of 
the  steam  which  would  be  used  at  boiler  pressure,  while  F  H  is  the  amount 
used  at  the  reduced  pressure.  The  line,  L,  is  simply  an  extension  in  order  to 
carry  out  the  curve  a  little  further  and  see  precisely  where  it  would  strike. 


LESSON  XXXVIII. 


IT  is  really  refreshing  to  turn  from  bad  engineering,  such  as  we  have  illus- 
trated in  some  of  our  previous  lessons,  to  an  approximatively  good  practice, 
where  preferences  and  prejudices  have  been  laid  aside  and  ignorance  is 
ignored.  We  have  just  this  kind  of  a  case  in  this  lesson.  The  diagram  which 
is  shown  is  from  an  engine  24  inches  by  48,  running  58}^  revolutions,  55 
pounds  boiler  pressure,  taken  in  actual  work,  and  not  for  the  purpose  of 
exhibition.  This  engine  was  built  by  C.  H.  Brown  &  Co.,  of  Fitchburg, 
Mass.,  and  it  may  properly  be  said  that  Mr.  Brown  is  one  of  the  few  engine 
builders  in  this  country  who  has  adopted  the  Indicator  as  his  standard  to  work 
from  and  to  work  toward.  In  other  words,  if  his  Indicator  tells  him  his  ports 
are  too  small,  and  the  throw  of  his  valves  is  not  right,  he  has  had  the  good 
sense  to  adopt  that  as  his  standard,  and  endeavor  to  attain  all  that  the  Indi- 
cator suggests.  This  diagram  (Fig.  80)  shows  the  result  of  his  approaches. 

The  compression  in  this  engine  is  easy,  and  gives  a  graceful  line;  the 
steam  valve  opens  as  the  compression  ends,  and  fills  the  cylinder  without  there 
being  any  hitch  in  the  line.  When  the  piston  starts  on  its  stroke,  steam  is 
carried  for  a  little  period  of  time  at  full  boiler  pressure,  then  it  commences  to 
fall  off  a  trifle,  as  at  B ;  from  B  to  C  it  falls  nearly  two  pounds.  The  reason 
of  this  is  found  in  the  fact  that  when  the  piston  starts  from  the  dead  center  on 
the  crank,  or  from  the  very  commencement  of  its  stroke,  its  motion  is  very 
slow;  after  it  has  proceeded  a  very  short  distance,  the  speed  is  decidedly 
accelerated,  and  the  pressure  is  slightly  reduced,  —  a  little,  indeed,  —  but  in 
practical  working  it  is  of  no  possible  consequence,  either  as  to  perfection  or 
economy.  When  the  valve  closes  the  line  is  distinctly  formed,  and  we  know 
just  where  to  figure  in  attempting  to  work  for  the  quantity  of  steam  consumed 


TWENTY  YEARS    WITH  THE  INDICATOR.  131 

or  to  lay  out  the  theoretical  curve.  The  corner  of  this  is  not  rounded  off  like 
the  circle  made  by  a  coach-and-four  in  making  a  turn.  We  can  put  our  finger 
definitely  upon  the  very  point  where  the  valve  commenced  to  close,  and  where 
it  did  close,  —  there  is  no  guess-work  or  assumption,  —  and  we  do  not  have  to 
begin  backward  or  at  the  end  of  the  expansion  curve  and  guess  that  the  valve 
did  not  leak,  or  suppose  that  the  steam  did  not  do  something  else. 

The  line,  A,  is  drawn  slightly  above 
boiler  pressure,  in  order  that  it  may  not 
merge   into   the  steam   line  proper;    and 
when  we  say  that  98^   per  cent,  of  the 
boiler  pressure  is  admitted  into  the  cylin- 
der, we  only  state  a  simple  fact,  and  one 
which  our  readers,  who  have  been  working 
with  60,  70,  or  80  per  cent,  of  the  boiler 
pressure,  will  not  be  slow  to  put  its  proper 
value  on.     The  expansion  line  of  this  card 
is  very  fine ;  its  exhaust  is  as  near  perfect 
as  we  need  to  expect,  and,  taken  all  in  all, 
it  is  certainly  a  model  card.     We  do  not 
know  the  clearance  of  the  engine,  or  we 
would  have  elaborated  it  somewhat.   When 
dealing  with  this  subject,  however,  we  pre- 
fer to  have  the  absolute  fact  of  the  clearance 
either  from  measurement  or  the  builder's 
plan,   and   sometimes   we    take    pains    to 
corroborate  the  builder's  estimate  from  the 
measurement.     This  card  was  taken  from 
one  of  a  pair  of  engines  while  it  was  at 
work  in  the  middle  of  the  day,. with  no 
preparation  or  readjustment  of  valves,  for 
the  purpose  of  ascertaining,   more   than 
anything  else,  how  near  it  approached  to 
boiler  pressure.    The  experiment  was  after- 
ward conducted  by  making  vertical  lines 
with  the  Indicator,  and  then  taking  a  dia- 
gram across  these  lines  to  ascertain  whether 
the  Indicator,  the  steam  gauge,  and   the 

cylinder  pressure  agreed.  The  pressure  in  the  cylinder  with  this  experiment 
covered  the  top  of  the  vertical  lines  by  the  steam  line  at  a  slightly  lower 
pressure  than  the  one  shown,  so  perfectly  as  to  make  complete  union  by  the 
steam  lines  crossing  the  very  end  of  the  vertical  line  while  the  Indicator 
cylinder  was  at  rest.  This  engine  has  been  running  some  two  years  and  it  is 
under  the  care  of  an  engineer  who  takes  good  care  to  adjust  the  valves  of  his 


i32  TWENTY  YEARS    WITH  THE  INDICATOR. 

engine  with  his  own  Indicator,  and  he  believes  that  the  nearer  to  perfection 
he  can  bring  it,  the  nearer  he  is  doing  his  duty  by  his  employer,  and  parties 
visiting  his  engine  room  will  find  things  as  nice  and  clean  as  though  he  was  in 
a  library  rather  than  an  engine  room.  Oil  and  gurry  are  not  found  burnt  on 
to  his  engine,  the  brass  and  nickel  work  are  as  bright  as  a  new  looking-glass, 
and  the  owner  of  the  engine  finds  that  it  costs  less  to  employ  a  first-class  man, 
when  all  things  are  taken  into  account,  than  it  does  to  employ  what  are 
frequently  spoken  of  as  tramps.  There  is  economy  in  this  card,  as  well  as 
perfection,  and  if  those  of  our  readers  who  are  interested  will  figure  it  care- 
fully, they  will  find  that  the  figures  run  up  into  the  nineties  all  round. 


LESSON   XXXIX. 


WE  are  frequently  shown  cards  from  the  Indicator  which  develop  most 
astounding  approximations  to  the  theoretical  value  of  steam,  but  the  best  way 
to  get  at  this  practically  is  to  take  cards  or  diagrams  from  the  every-day 
working  of  the  machine,  and  then  ascertain  whether  the  machine,  in  its  every- 
day work,  can  and  will  do  what  these  expert  or  scientific  builders  frequently 
assert  they  can  do.  Having  this  thing  in  mind,  we  have  taken  the  card, 
which  is  the  subject  of  this  sketch,  out  of  a  complete  set,  which  were  not 
taken  for  adjustment  of  valves,  or  for  any  other  especial  purpose  beyond  that 
of  ascertaining  the  precise  condition  of  the  engine.  It  is  from  one  of  a  pair 
of  large  Corliss  engines,  now  working  in  Fall  River.  The  size  is  28  X  60,  54 
revolutions,  40  scale,  boiler  pressure  87  pounds  by  the  gauge.  The  line,  A,  is 
the  atmospheric  line  of  the  instrument;  B,  actual  vacuum  ;  C,  boiler  pressure, 
including  actual  vacuum ;  D,  boiler  pressure ;  E,  end  of  the  stroke,  or  what 
should  be  the  admission  line ;  F,  the  long  dotted  line,  the  theoretical  curve 
from  the  actual  point  of  cut  off,  as  seen  on  the  card ;  G,  fine  dotted  line,  the 
actual  line  of  the  instrument.  The  admission  line  plainly  shows  that  the  valve 
does  not  open  early  enough,  and,  as  a  matter  of  fact,  nearly  two  inches,  after 
the  piston  has  begun  on  its  stroke,  is  accomplished  before  the  valve  is  wide 
open.  The  steam  line,  therefore,  falls  away  from  the  actual  boiler  pressure  3^ 
pounds.  We  have  no  data  to  say  how  far  the  steam  travels  from  the  boilers. 
The  cut  off  is  very  sharp,  and  the  expansion  line  is  very  good.  It  will  be 
noticed  that  our  cut  off  point,  as  taken  from  the  instrument,  should  have  been 
carried  a  little  farther  on  the  stroke.  We  have  assumed  it  a  trifle  longer  than 
it  really  is,  but  taking  this  for  data,  in  all  the  computations  which  follow,  is  a 


TWENTY  YEARS    WITH  THE  INDICATOR.  133 

little  against  the  engine  rather  than  in  its  favor,  taking  absolute  facts,  from 
which  our  computations  are  made. 

The  exhaust  valve  of  this  engine  does  not  open  as  early  as  it  should,  by 
fully  two  inches  of  the  stroke  of  the  engine ;  it  does  not  open  early  enough, 
and  the  condenser,  therefore, 
does  not  obtain  the  amount  of 
vacuum  it  should  and  will  do  if 
they  will  open  it  early  enough. 
At  the  other  end  of  the  stroke 
there  is  very  little  compression 
indeed,  in  fact,  none  of  any 
amount,  and  opening  the  ex- 
haust valve  earlier,  allowing  the 
condenser  to  do  its  work  more 
efficiently,  would  make  com- 
pression at  the  end  of  the 
stroke,  which  would  be  favoring 
the  engine,  and  compression 
can  be  obtained  on  a  condens- 
ing engine,  notwithstanding 
statements  to  the  contrary  by 
men  who  style  themselves  ex- 
perts or  engine  builders. 

The  distance  between  the 
lines,  C  and  E,  is  the  actual 
measure  of  the  clearance  of  that 
end  of  the  cylinder  from  which 
this  card  was  taken  ;  the  volume 
of  space,  including  both  valve 
ports,  amounts  to  1.71  inches; 
in  our  figures  we  have  included 
the  clearance  of  the  engine. 
The  clearance,  and  the  distance 

which  steam  is  carried,  amounts  to  T2T\  of  the  whole  stroke.  The  Planimeter 
gives  us,  including  the  boiler  pressure,  the  full  space  of  the  theoretical  curve, 
an  absolutely  perfect  vacuum,  and  a  compression  of  one-tenth  the  stroke,  not 
including  the  clearance,  444.  The  actual  line  denned  by  the  Indicator,  gives 
us  388,  or  87.4  per  cent,  of  the  theoretical,  including  all  the  outs  or  bad  features 
of  the  diagram.  If  the  engine  took  its  steam  properly,  and  exhausted  prop- 
erly, there  is  no  difficulty  whatever  in  making  this  engine  do  92  to  94  per  cent, 
of  the  theoretical,  and  doing  it -from  the  coal-pile,  and  not  from  any  one's  ideas. 
If  the  engine  took  steam  quicker,  we  should  save  the  area  between  the  lines, 
E,  and  the  admission  line  or  fine  dotted  line,  and  this  would  shorten  the  space 


134  TWENTY  YEARS    WITH  THE  INDICATOR. 


which  steam  is  carried,  so  that,  instead  of  being  ^f^,  it  would  probably  run 
down  to  22  or  23,  and  the  very  fact  of  opening  this  valve  earlier  would  allow 
more  steam  to  enter  this  cylinder,  and  would  give  us  nearer  actual  boiler 
pressure  ;  hence  the  displacement  of  the  steam  valve  of  the  engine  is  working 
decidedly  against  its  economy.  If  the  exhaust  valve  opened  earlier,  the  con- 
denser could  do  its  work  better,  because  it  would  take  the  bulk  of  the  steam 
quicker,  and  would  make  a  more  effective  vacuum  or  a  nearer  approach  to 
complete  vacuum.  Therefore,  when  we  say  the  engine  is  doing  87.4  per  cent. 
of  the  theoretical,  we  do  not  say  that  the  engine  is  doing  all  that  it  will  or  all 
that  it  can  ;  but,  taking  the  card  precisely  as  it  came  from  the  Indicator,  and 
just  as  the  engineer  was  running  the  engine,  in  the  face  of  very  apparent  dis- 
advantages, which  could  and  ought  to  be  remedied  by  the  proper  application 
of  the  Indicator,  it  is  then  doing  almost  90  per  cent,  of  the  theoretical.  In 
doing  this,  the  displacement  of  the  steam  valve  loses  3^  pounds  boiler 
pressure,  the  condenser  gives  us  108  or  no,  while  in  the  theoretical  we  figure 
150  to  155,  the  condenser  only  doing  75  per  cent,  of  the  theoretical  —  this  in 
the  total  figures  against  the  engine.  If  we  take  the  high  pressure  part  of  the 
diagram,  and  suppose  the  engine  would  exhaust  as  these  engines  usually  do, 
we  should  have  88^  per  cent,  actually  developed  by  Planimeter  measurement. 
The  steam  valve  of  the  engine  should  be  quickened  considerably,  and  the 
exhaust  valve  quickened  also  ;  this  means  moving  the  eccentric  ahead  on  the 
shaft  from  an  inch  to  an  inch  and  a  quarter  ;  then  perhaps  the  jim-cranks  may 
have  to  be  lengthened  or  shortened,  as  the  case  may  be,  in  order  to  bring  the 
other  valves  up  to  time.  There  is  a  point  where  half  a  turn  on  the  jim  -crank, 
or  a  quarter  of  an  inch  on  the  eccentric  forward  or  back,  makes  a  radical 
difference.  Eighty-two  pounds  in  the  cylinder,  with  87  in  the  boiler,  and  the 
steam  valve  opening  two  inches  behind  the  piston,  is  a  better  showing  than  a 
great  many  engines  make. 

The  man  running  this  engine  should  open  his  steam  valve  so  that  it  would 
touch  the  line,  E,  where  the  dotted  portion  is  at  the  bottom,  quite  up  until  the 
steam  line  is  commenced.  These  changes  are  simple,  and,  with  the  Indicator 
can  be  readily  made.  Where  the  point  of  cut  off  is  so  thoroughly  defined,  as 
in  this  case,  there  is  no  difficulty  whatever  in  following  the  lines  from  the  point 
of  cut  off,  not  from  the  termination  of  the  expansion  line. 

This,  as  are  all  our  diagrams,  is  exactly  full  size,  and  can  be  measured  and 
worked  from  by  any  of  our  readers  who  are  so  disposed.  This  will  be 
interesting  for  them  ;  it  is  good  practice  ;  it  deals  only  in  facts,  and  it  will  show 
them  how  to  apply  the  rules,  which  any  one  can  do,  and  how  to  ascertain 
whether  the  engine  does  what  the  builder  represents,  especially  where  they  are 
loud  in  decrying  well-established  precedents  by  other  builders.  Facts  are  not 
always  agreeable,  but  they  are  the  best  things  in  the  world  from  which  to 
obtain  information,  and  they  sometimes  take  the  conceit  out  of  people,  even 
if  at  considerable  cost,  and  are  to  sensible  men  invaluable. 


TWENTY  YEARS   WITH  THE  INDICATOR.  135 


LESSON  XL. 

As  a  fitting  close  to  the  practical  lessons  embodied  in  this  volume,  we 
introduce  one  of  the  most  radical  departures  in  steam  engineering,  and  one  of 
the  most  successful  of  the  almost  numberless  candidates  working  in  the  direc- 
tion of  high  speed.  This  engine  is,  to  a  certain  extent,  an  anomaly,  and 
in  Volume  II.,  which  will  complete  this  work,  we  hope  to  embody  the 
valves  and  valve  motion,  and  the  regulator  with  its  full  line  of  action,  so  that 
our  readers,  who  do  not  become  discouraged  in  this  volume,  can  gather  from 
them  what  has  been  attained  by  a  careful  keeping  in  view  of  the  theoretical 
value  of  steam  after  it  is  made,  and  the  practical  working  out  of  the  largest 
percentage  of  that  theoretical  value,  which  has,  as  yet,  we  believe,  been  attained 
by  any  high  speed  engine. 

Figs.  82,  83,  and  84,  were  all  taken  from  the  Armington  &  Sims  engine, 
on  the  same  day,  under  varying  conditions.  The  size  of  the  engine  was  9^ 
inches  diameter  of  piston,  12  inches  stroke,  300  revolutions  per  minute, 
boiler  pressure  varying  from  85  to  82  pounds,  scale  60. 


FIG.  82. 

Diagram  A  represents  the  engine  as  working  at  80  horse-power  indicated, 
with  an  average  pressure  of  56.51  pounds.  The  admission  line  is  almost 
absolutely  perfect.  There  is  a  trifling  variation,  probably  caused  by  the  piston 
of  the  Indicator.  The  steam  line  is  simply  perfect,  cutting  off  at  a.  The 
expansion  line,  under  such  a  speed,  is  slightly  waved  ;  and  this,  without  doubt, 
is  somewhat  owing  to  the  intensity  in  the  action  of  steam  and  the  impulse  of 
the  momentum  of  the  Indicator.  The  variations  are,  however,  very  slight, 
when  the  speed  is  considered,  and  the  mechanical  perfection  required  both  in 
the  valves  of  the  engine  and  in  the  piston  of  the  Indicator.  The  release,  at  &,' 
approximates  closely  to  locomotive  practice;  the  commencement  of  the 
exhaust,  at  £,  shows  a  back  pressure  of  between  one  and  two  pounds  at  the 
commencement,  and  about  one  pound  at  the  termination.  The  cushion,  or 
compression,  on  this  engine,  owing  to  its  very  high  speed,  is  not  precisely  of 


136  TWENTY  YEARS    WITH  THE  INDICATOR. 

the  same  character  as  in  the  slower  moving  engine,  the  line  being  somewhat 
irregular.  The  peculiar  points  of  this  diagram  will  be  noticeable  by  every 
steam  engineer  when  he  considers  that  it  was  completed  in  one-tenth  of  one 
second  while  running  at  regular  speed.  This  diagram,  taken  all  in  all,  is  one 
which  embodies  a  very  high  economy  with  an  almost  perfect  regulation. 

Diagram  B  is  the  same  engine  precisely,  developing  52.08  horse-power, 
with  an  average  pressure  of  36.83  pounds.  In  this  case  we  have  not  lost  any 
of  the  beauty  of  the  steam  or  admission  lines.  As  in  diagram  A,  the  expan- 
sion line  has  a  somewhat  more  wavy  appearance,  the  release  commences 
almost  at  the  same  point,  —  if  anything,  a  trifle  earlier,  —  and  the  compression 
being  comparatively  earlier,  coinciding  with  the  release.  Diagram  A  has  85 
pounds  boiler  pressure,  and  81  pounds  by  the  Indicator  in  the  cylinder. 
Diagram  B  has  85  pounds  boiler  pressure,  and  82  pounds  in  the  cylinder, 
while  diagram  C  has  80  pounds  in  the  cylinder,  with  an  indicated  horse-power 
of  11.78,  and  a  mean  pressure  of  8.33  pounds. 


Parties  who  will  study  these  three  diagrams  will  see  that  the  release  and 
compression  vary  materially,  and  on  these  points  it  is  well  to  say  that  this  is 
the  first  engine  we  have  ever  noticed  which  worked  steam  according  to  the 
theory  of  expansion  and  compression,  as  approaching  most  nearly  the  produc- 
tion of  the  largest  amount  of  utilized  units  of  heat  from  the  steam ;  in  other 
words,  the  regulator  and  valve  motion  of  this  engine  are  so  arranged  that  the 
valve  has  an  absolutely  constant  motion,  with  reference  to  giving  the  engine 
steam,  but  every  other  position  of  the  valve  is  variable  according  to  the  load, 
and  in  the  case  of  release  and  compression,  these  two  important  and  often 
overlooked  points  are,  by  the  inventors  and  builders  of  this  engine,  made  to 
vary  inversely  as  to  the  load. 

Diagram  C  gives  us  the  nearest  approximation  to  what  our  old  friend, 
Prof.  Thurston,  of  the  Stevens  Institute  of  Technology,  has  long  argued  was 
the  correct  way  of  working  steam ;  that  is,  that  steam  at  a  certain  pressure 
and  temperature  should  be  expanded  that  number  of  times  which  would  make 
it  most  efficient,  and  which,  without  any  exhaust,  could  be  compressed  on  the 
return  stroke,  making  another  line  lower  in  utilic  effect  than  the  first,  and 
needing  only  a  small  amount  of  steam  to  make  it  do  the  second  and  each 


TWENTY  YEARS    WITH  THE  INDICATOR.  137 

successive  stroke.  Armington  &  Sims,  in  this  case,  have  so  arranged  the 
motions  of  their  valves  that  the  load  upon  the  engine  varies  the  amount  of 
steam  admitted,  and  the  amount  of  the  load  governs  the  release  and  exhaust 
inversely ;  that  is,  in  opposition  to  the  regular  proportion,  the  greater  the  load 
the  later  release  and  compression ;  the  lighter  the  load,  the  earlier  release  and 
compression ;  hence,  we  have,  in  diagram  C,  a  release  somewhere  about  plus 
one-half  the  stroke,  and  a  compression  of  slightly  minus  one-half  the  stroke. 
By  this  mode  of  compression  one  of  the  greatest  antagonisms  to  the  success 
of  high  speed,  in  practice,  has  been  overcome ;  that  is,  the  loss  of  steam  and 
the  expense  of  maintaining  a  large  clearance. 

Diagram  C,  it  will  be  seen,  compresses  56  pounds ;  the  steam  valve  then 
opens  and  the  admission  and  steam  lines  are  almost  at  absolutely  right  angles 
to  each  other.  The  larger  the  load  the  later  the  release  and  compression,  but 
the  engine  exhausts  freely  up  to  that  load,  which  is  the  maximum  ;  and  when 


FIG.  84. 

the  engine  is  running  almost  without  load,  the  release  and  compression  are  so 
arranged  that  no  thumping  or  jar  occurs  to  the  machine.  This  is  the  highest 
attainment  toward  working  steam  expansively.  It  is  done  by  a  single  piston 
valve  controlled  by  a  variable  regulator,  the  engine  furnishing  the  power,  the 
regulator  changing  its  movements  according  to  the  increase  or  decrease  of  the 
load,  varying  from  ten  to  eighty  horse-power  on  perhaps  three  strokes  of  the 
engine  without  making  a  change  of  more  than  three  or  four  revolutions,  or 
affecting  the  speed  for  more  than  one-half  to  three-quarters  of  a  second. 
These  diagrams  will  bear  a  great  amount  of  study,  and  practical  engineers 
cannot  fail  to  admire  them. 


138  TWENTY  YEARS  WITH  THE  INDICATOR. 


LESSON  XLI. 


DEMONSTRATING  THE  ACTUAL  POINT    OF  CUT-OFF  FROM  THE    STEAM 
USED,  WITHOUT  REGARD  TO  TERMINAL  PRESSURE  OR  LACK 
OF    DISTINCTNESS  IN  THE   CUT-OFF    LINE. 

In  our  own  experience,  we  have  frequently  been  unable  to  determine  the 
point  of  cut-off  with  sufficient  accuracy  or  reliability,  wherever  the  line  of  the 
diagram  was  not  clearly  denned,  and  this  oftentimes  becomes  necessary  in 
making  computations,  or  in  comparing  one  engine  with  another  for  efficiency. 
It  was,  therefore,  after  considerable  investigation,  that  we  adopted  the 
method  first  published  by  the  writer,  September  15th,  1883,  as  a  method 
of  demonstrating  the  positive  point  at  which  steam  is  cut  off,  or  a  point 
on  the  line  of  initial  pressure  equal  to  cutting  off  steam  at  a  particular 
point,  even  where  a  leak  had  occurred,  or  where  steam  had  drifted  past  the 
steam  valve  after  it  was  supposed  to  be  closed.  At  that  time  we  used  the 
following  expression :  "  We  have,  therefore,  stolen  a  march  on  volume  two  of 
Twenty  Years  with  the  Indicator,  by  showing  the  mathematically  correct 
way  of  demonstrating  the  positive  point  at  which  the  steam  is  cut  off,  or  a 
point  which  is  equal  to  the  cutting  off  of  the  steam  at  some  especial  or 
particular  point  whenever  steam  leaks  or  drifts  in." 

Since  this  statement  was  made,  this  method  has  been  examined  by  some 
of  the  best  mathematicians,  and  has  been  pronounced  correct.  It  will  be 
referred  to  in  the  following  lessons  in  this  volume  as  the  demonstration  or 
our  demonstration.  We  reproduce  the  original  diagrams,  now  in  our  pos- 
session, which  were  published  with  this  first  demonstration. 

It  has  been  customary  in  years  past  for  builders  of  engines,  engineers 
and  experts  to  erect  then*  comparison  from  the  "  axis  of  the  hyperbola,"  or 
from  the  terminal  pressure.  "  The  axis  of  the  hyperbola  "  is  an  indefinite, 
uncertain  quantity,  and  the  terminal  pressure  is  as  apt  to  be  wrong  as  right, 
and  we  wish  to  impress  upon  the  reader  of  this,  that  in  this  case  we  divide 
the  problem  into  two  different  and  distinct  demonstrations ;  first,  we  locate  the 
exact  point  of  cut-off  on  the  line  of  initial  or  realized  pressure  in  the  cylinder, 
from  a  point  a  little  past  or  "at  the  center  of  the  expansion  line  of  the  diagram. 
The  reason  why  we  do  this  is  that  at  or  a  little  past  the  center  of  the  expan- 
sion line,  the  steam  has  become  more  settled  in  its  action,  is  less  liable  to 
irregular  pressure,  the  speed  of  the  piston  is  nearer  constant,  and  the  load 
affects  least  either  the  piston  or  the  crank  in  overcoming  the  resistance,  on 
the  same  principle  that  a  train  of  cars,  after  in  motion,  gives  a  better  idea  of 
the  actual  load  than  when  starting  or  stopping  them.  This  point,  wherever 
located,  is  termed  the  base  line  of  the  demonstration.  This  method  is 
founded  upon  the  principle  that  if  the  pressure  at  a  given  point  is  known, 


TWENTY  YEARS  WITH  THE  INDICATOR.  139 

and  if  steam  does  expand  somewhere  near  Mariotte's  law,  then  it  becomes  a 
mathematical  problem,  and,  if  we  know  the  pressure  at  a  certain  point,  we  can 
lay  out,  by  the  means  to  be  explained,  the  precise  point  at  which  a  known 
initial  pressure  of  steam  should  be  cut  off  to  realize  the  pressure  denoted  by 
the  base  line  wherever  it  is  located.  This  is  the  whole  theory  and  it  has  been 
reduced  to  practice  in  so  many  different  forms  of  diagrams,  at  so  many  dif- 
ferent points  of  cut-off,  under  so  many  different  pressures,  and  with  such  a 
variety  of  types  of  engines,  that  the  best  authorities  in  several  of  our  insti- 
tutions of  learning  have  adopted  it,  and  have  pronounced  it  mathematically 
correct.  We  do  not  mean  to  go  into  mathematics  to  any  extent,  and  shall, 
therefore,  refer  our  readers  to  the  various  diagrams  illustrated  in  this  volume, 
which  are  founded  upon  this  demonstration,  and  which  embrace  a  large  range 
of  different  types  of  engines  at  all  sorts  of  speed,  under  all  differences  of 
pressure,  and  that  the  comparisons  made  are  actual  rather  than  visionary. 

Very  frequently,  as  in  one  of  the  first  examples  given  in  this  lesson,  we 
have  found  the  apparent  or  visible  cut-off,  on  the  diagram  as  made  by  the 
instrument,  to  vary  materially  from  the  demonstrated  line.  To  explain  this 
briefly,  it  frequently  occurs  that  the  valve  does  not  seat  itself,  or  that  some 
disturbance  occurs  in  its  action,  so  that  after  it  is  apparently  closed  and  the 
expansion  line  has  been  commenced,  that  a  quantity  of  steam  drifts  into  the 
cylinder,  so  that  the  indicator  does  not  make  a  true  expansion  line  from  the 
quantity  of  steam  shown  by  the  visible  point  of  cut-off,  and  this  method 
shows  us  precisely  the  amount  of  steam  wasted  as  between  visible  and 
demonstrated  points  of  cut-off.  We  have  never  yet  found  an  engine  with  this 
demonstration  where  the  actual  line  of  the  indicator  overran  in  amount  of 
work  yielded,  the  theoretical  line  drawn  from  the  point  of  cut-off  from  the 
demonstration. 

Another  point  for  the  reader  which  may  be  asked,  we  will  anticipate.  It 
is  frequently  necessary  (in  his  mind  only,  however,)  to  know  precisely  the 
amount  of  clearance  to  an  engine,  in  order  to  know  exactly  the  use  of  the 
steam.  With  this  method  of  demonstration  the  clearance  becomes  unnecessary 
so  far  as  the  demonstration  goes ;  it  is  very  important,  however,  if  we  are 
figuring  the  diagram  for  economy  in  water,  to  know  the  clearance,  but  so  far 
as  the  action  of  steam  goes,  and  the  reliability  of  the  demonstration  based  on 
that  action,  the  clearance  is  an  unnecessary  quantity.  We  are  dealing  with 
the  steam  after  the  expansion  takes  place,  it  shows  us  what  the  valves  do  and 
shows  it  correctly,  but  if  we  are  to  get  at  the  actual  amount  of  steam  used,  in 
every  instance,  we  must  then  learn  the  clearance  of  the  engine  and  add  a  pro- 
portionate length  to  the  amount  of  steam  used ;  but  these  two  elements  are 
not  of  necessity  identified  with  each  other  so  that  the  clearance  need  to  be 
taken  into  account  in  the  demonstration. 

Fig,  96  is  taken  from  a  Corliss  engine,  which  has  been  running  many 
years.  To  explain  our  demonstration,  we  first  of  all  draw  the  line  of  initial 
pressure  C,  then  the  line  of  absolute  vacuum  D,  the  vertical  line  B,  which  in 
this  case  represents  the  clearance  of  the  engine.  We  have  now  actually 
known  factors.  Now,  at  some  point  in  the  expansion  line,  in  this  case  at  the 


140 


TWENTY  YE  ARK  WITH  THE  INDICATOR. 


crossing  of  the  expansion  line  with  the  line  of  rest  of  the  instrument,  we 
draw  the  vertical  line  A  ;  this  is  also  a  known  quantity  ;  it  is  the  actual  press- 
ure in  the  cylinder  above  the  vacuum  line,  it  is,  therefore,  a  known  quantity. 
There  is  no  especial  reason  why  we  locate  it  at  this  particular  point  in  the 
stroke,  only  at  that  point  the  line  is  entirely  settled  in  its  work. 

Now,  from  the  intersection  of  A,  D,  we  draw  the  angular  line  E,  which 
connects  the  base  of  A  with  the  intersection  of  B,  C,  at  the  point  represent- 
ing the  clearance  of  the  engine  added  to  the  diagram  and  the  initial  pressure. 
This  line  is  for  the  purpose  of  demonstration ;  now  we  wish  to  obtain  a 
parallel  line  to  the  one  just  erected ;  measure  the  distance  from  A  to  the  line 
just  erected  on  the  atmospheric  line,  as  in  this  case  the  top  of  the.  line  A 
intersects  with  the  atmospheric  line ;  lay  off  this  distance  A,  E,  on  C  which 
gives  the  distance  F,  I ;  lay  off  the  same  distance  on  the  line  D,  which  gives 
us  D,  K,  or  from  the  base  line  A  to  the  new  line  K,  F.  F  is,  therefore,  the 


FIG.  96. 

point  at  which  the  initial  pressure  of  steam  should  have  been  cut  off  to  have 
given  the  pressure  A  at  that  point  in  the  expansion  line.  It  will  be  seen  that 
the  fact  and  the  demonstration  do  not  agree  apparently.  This  is  the  end  of 
the  demonstration  practically.  Now,  if  we  compare  results,  we  find  that  the 
lines  of  the  indicator  diagrams,  as  left  by  the  instrument,  show  a  very  much 
shorter  cut-off  than  the  line  F.  But,  at  the  point  J,  the  theoretical  curve 
dropped  from  the  line  F,  joins  with  the  actual  line  of  the  instrument,  and 
from  the  point  J  the  theoretical  and  the  actual  run  on  together.  After  the 
valve  in  the  engine  closes,  an  amount  of  steam  passed  through  under  it  and 
was  carried  into  the  cylinder,  and  the  amount  of  steam  increased  after  the 
cut-off  was  shown  by  the  indicator  to  equal  the  amount  shown  by  the  shaded 
portion  of  the  diagram,  between  the  actual  line  of  the  instrument  and  the 
theoretical  line  dropped  from  F,  continuing  H,  J,  or  about  twenty  per  cent. 
The  point  F  represents  the  point  of  cut-off  equaling  the  actual  amount  of 


TWENTY  YEARS  WITH  THE  INDICATOR. 


141 


steam  put  into  the  cylinder,  taking  the  whole  diagram  into  account  as  demon- 
strated. The  steam  drifted  into  the  cylinder  from  the  time  the  cut-off  valve 
was  apparently  closed,  as  shown  by  the  indicator,  up  to  that  point  in  the 
stroke  represented  by  J,  where  the  leakage  stopped,  the  valve  then  had  be- 
come positively  closed  and  no  more  steam  was  admitted. 

It  may  be  remarked  that,  after  this  demonstration  had  been  published, 
the  agent  of  the  mill  from  whose  engine  this  diagram  was  taken  was  written 
to,  asking  him  if  he  would  examine  his  engine  to  see  whether  the  valve  on  the 
head  end  was  leaking  or  not.  His  answer  was : 


Yours  of- 


-receivecl :  contents  noted.     I  removed  the  cylinder 


head  last  night,  and  found  a  bad  leak  in  the  steam  valve." 

In  contrast  to  this,  we  introduce  Fig.  97,  taken  from  the  Pullman  engine 
at  the  Pullman  Car  Works,  near  Chicago;  the  same  engine  which  was 
exhibited  at  the  Philadelphia  Exhibition  in  1876,  by  Geo.  H.  Corliss. 

In  this  case  we  erect  first  the  line  of  initial  

pressure,  then  the  vacuum  line.  In  this  case  the 
clearance  is  not  known,  and  in  contrast  with 
Fig.  96  we  make  our  base  line,  A,  below  the  at- 
mospheric line.  The  demonstration  is  then  made 
precisely  as  in  the  former  case,  with  the  result 
that  the  motion  of  the  valve  in  this  case  is  a  trifle 
slow  as  compared  to  the  stroke,  and  the  visible 
and  actual  points  of  cut-off  vary  slightly,  but 
come  together  at  the  point  J,  which  in  this  case 
is  much  nearer  the  commencement  of  the  stroke. 


FIG.  97. 

The  actual  and  theoretical  then  run  along  almost  identically.  It  will  be  noticed 
that  there  is  nothing  assumed  in  this  case,  and  if  the  demonstration  is  care- 
fully made,  which  anyone  can  do  with  a  pair  of  triangles,  you  will  get 
positive  results.  F,  I,  in  this  case  represent  the  amount  of  steam  introduced 
into  the  cylinder.  The  expansion  line  runs  considerably  below  the  atmos- 
pheric line,  and  the  vacuum  line  is  almost  a  perfect  line,  there  being  no 
compression.  The  admission  line  is  parallel  to  the  vertical  by  its  side,  but 
the  opening  valve  is  a  very  trifle  late ;  or,  we  might  say  properly,  is  a  trifle 
slow  in  its  motion,  so  that  a  very  slight  diminution  of  pressure  is  observed. 
The  convexity  at  H  in  this  diagram  is  caused  by  a  slight  leak  in  the  valve 
when  it  seats.  It  must  be  borne  in  mind  at  this  time  that  the  expansion  is 


142  TWENTY  YEARS  WITH  THE  INDICATOR. 

in  a  very  rapid  ratio,  and  when  J,  the  expansion  line,  has  been  reached,  the  valve 
is  seated  and  not  another  particle  of  steam  obtains  access  into  the  cylinder. 
During  the  time  of  this  leak,  which  is  insignificant,  the  engine  makes  but 
trifling  progress  in  its  stroke.  From  the  point  J  to  the  termination  of  the 
expansion  line,  there  is  a  variation  of  less  than  one-fifth  of  one  per  cent,  from 
the  theoretical,  taking  into  account  the  realized  boiler  pressure  there  is  a  loss 
of  1.7  per  cent.  This  engine  is,  therefore,  realizing  98.3  per  cent,  of  the 
theoretical,  taking  realized  steam  pressure  as  the  unity. 

In  these  two  diagrams  we  have  avoided  any  confusion  of  lines  in  laying 
out  the  theoretical  curve.  That  method  will  be  explained  in  the  following 
diagrams,  and  if  the  readers  of  this  will  follow  the  different  examples,  show- 
ing the  adaptation  of  this  demonstration,  they  cannot  fail,  we  believe,  to 
become  as  proficient  and  as  careful  in  the  application  of  the  demonstration 
and  the  theoretical  curve,  as  anyone  need  to  be  for  all  practical  purposes.  By 
this  method  of  demonstration  we  show,  in  the  case  of  Fig.  97,  98  per  cent, 
plus,  while  in  Fig.  96  we  show  a  little  less  than  80  per  cent,  of  the  theoretical. 
Either  of  these  diagrams,  without  any  demonstration  upon  them,  make  a  fine- 
looking  curve;  it  shows,  therefore,  that  the  application  of  some  system  of 
demonstration  with  a  basis  of  fact,  will  give  us  what  we  are  studying  the 
indicator  for — actual  information  with  regard  to  some  thorough  and  reliable 
test,  to  ascertain  whether  the  diagrams,  after  taken,  if  good-looking,  shall 
give  us  practical  results,  showing  an  economy  in  the  use  of  steam  as  well  as 
a  pleasing  appearance  by  comparison. 

To  embody  the  whole  matter  for  reference,  we  give  the  following 

DIRECTIONS  FOR  MAKING  THE  DEMONSTRATION. 

Take  any  indicator  diagram,  lay  out  upon  it  the  absolute  vacuum  line 
with  the  scale  that  the  diagram  was  taken  with.  Then  lay  out  the  initial  or 
realized  pressure  in  the  cylinders ;  these  two  lines  will,  of  course,  be  parallel. 
Then  connect  these  two  lines  at  the  admission  end  of  the  diagram  by  a  verti- 
cal line  at  right  angles  to  the  two  horizontals  already  laid  down.  If  the 
clearance  is  known,  this  line  may  include  it,  otherwise  erect  it  simply  the 
width  of  a  line  away  from  any  portion  of  the  admission  line ;  but  this  may  be 
varied  somewhat ;  if  the  engine  takes  steam  too  early  or  too  late,  let  the 
vertical  line  barely  be  outside  of  the  extreme  point  covered  by  the  line  of  the 
indicator.  Now,  from  some  point  on  the  expansion  line  near  the  center,  if 
anything,. a  little  beyond,  erect  the  base  line  from  the  actual  line  of  the 
indicator  to  the  absolute  vacuum  line,  and  be  careful  to  have  it  at  right  angles 
to  the  vacuum  line.  From  the  intersection  of  this  line  with  the  vacuum  line, 
draw  a  diagonal  to  the  intersection  of  the  steam  pressure  and  vertical  line. 
Now,  by  means  of  a  triangle  lay  off  a  right-angled  line  from  the  top  of  the 
base  line,  or  its  intersection  with  the  expansion  line  of  the  diagram,  until  it 
intersects  with  the  diagonal  line  just  drawn.  The  purpose  of  this  line  is  to 
measure  carefully,  with  a  pair  of  dividers  or  otherwise,  the  distance  from  the 
top  of  the  base  line  to  the  diagonal,  so  that  this  distance  may  be  transferred 


TWENTY  YEARS  WITH  THE  INDICATOR.  143 

both  to  the  vacuum  line  and  the  steam  pressure  line,  as  the  exact  points 
from  which  to  draw  the  parallel  diagonal,  and  this  parallel  diagonal  line  must  in 
every  instance,  and  will  if  properly  done,  pass  by  the  exact  top  of  the  base 
line  at  the  point  of  its  intersection  with  the  expansion  line  of  the  instrument. 
"Wherever  this  line,  the  last  diagonal,  touches  the  line  of  steam  pressure,  from 
that  point  drop  a  perpendicular  to  the  vacuum  line.  You  have  now  the 
precise  point  of  cut-off  from  the  pressure  at  the  base  line,  or  first  line 
erected. 

These  instructions  apply  to  the  low  pressure,  condensing,  compound 
locomotive,  marine  or  any  other  indicator  diagram,  whether  taken  from 
steam,  water,  air,  gas,  so  far  as  we  have  ever  been  able  to  prove  it.  This  rule 
has  been  given  to  familiarize  the  reader,  and  without  any  letters  of  reference, 
so  that  the  principles  may  be  thoroughly  understood.  The  mathematical 
demonstration  is  not  necessary,  we  think,  from  the  explanation  which  has 
preceded  it.  The  clearance  should  always  be  used  in  demonstration  to  in- 
sure correct  results,  whether  for  simple  cut-off  or  any  computation;  it  makes 
a  certainty,  and  is  little  trouble,  compared  to  accuracy  of  result. 


LESSON   XLH. 


DEMONSTRATION  OF  THE  POINT  OF  CUT-OFF,  AND  HOW  TO  LAY  OUT 
THE  THEORETICAL  CURVE. 

Fig.  98  is  an  interesting  diagram  in  many  respects,  and  only  shows  what 
the  general  tendency  is  among  steam  users  by  overloading  their  engines. 
The  data  with  this  diagram  is  17  inches  diameter,  36  inches  stroke,  57  revolu- 
tions per  minute,  boiler  pressure  70,  scale  30.  A  is  the  absolute  vacuum ;  B, 
highest  realized  pressure  in  the  cylinder ;  C,  vertical  line  being  nominally  to 
represent  the  end  of  the  stroke,  clearance  not  included  in  this  case. 

Having  surrounded  the  diagram  by  a  parallelogram,  we  commence  by 
drawing  the  line  D,  which  represents  the  pressure  of  steam  above  absolute 
vacuum  at  that  point  of  63^  pounds  From  the  intersection  of  A  D,  E  is 
drawn  to  the  intersection  of  C  B.  Now,  from  the  top  of  the  line  D,  draw  at 
right  angles  the  dotted  line  J,  connecting  D  E ;  the  distance  from  one  end  to 
the  other  of  J  is  the  distance  to  be  laid  off  on  the  line  B,  as  well  as  A  for  the 
parallel  line,  F.  From  the  intersection  of  F  B  we  drop  G,  and  the  length 
of  the  line,  B,  from  C  to  G,  is  the  volume  of  the  cylinder  filled  with  steam  at 
the  initial  pressure,  which  should  be  cut  off  at  the  point  G  on  B  to  produce 
the  pressure,  D,  on  the  expansion  line.  This  finishes  the  demonstration  of  the 
point  of  cut-off. 


i44  TWENTY  YEARS  WITH  THE  INDICATOR. 

We  wish  now  to  erect  from  this  data  already  obtained  the  theoretical 
curve,  in  order  to  ascertain  whether  the  expansion  line  of  the  engine  approxi- 
mates closely  or  otherwise  to  the  theoretical  line.  We  repeat  here  the 
method  given  in  Volume  I,  and  shall  endeavor  to  explain  it  so  fully  that  no 
reference  to  Volume  I  will  be  required.  We  commence  at  the  intersection 
of  A  C,  drawing  the  radial  lines,  and  to  prevent  confusion,  we  have  used 
numerals  rather  than  letters  in  this  figure.  These  lines  are  drawn  from  the 
point  K  on  the  intersection  of  A  C.  In  erecting  the  theoretical  curve,  the 
base  of  our  computation  must  always  be  absolute  vacuum.  While  this  differs 
somewhat  in  barometrical  range,  it  is  exceedingly  small,  and  for  the  moment 
we  assume  it  at  14.7.  We  draw  the  lines,  1  from  K  to  G,  and  the  line  2  from 
•  K  to  the  end  of  the  line  B,  covering  the  very  end  of  the  diagram.  Now, 
between  these  two  lines,  1,  2,  on  B,  we  drop  the  ordinates  at  right  angles  to 
B,  a  little  below  the  expansion  line,  at  any  distance  apart  we  choose.  In  this 
case  we  drop  3,  4,  close  together;  then  5,  6,  7,  at  a  distance  double  that 
between  3  and  4.  There  is  no  special  reason  for  making  any  difference  in 
this.  We  sometimes  drop  the  ordinates  closer  together  in  the  first  part  of 
the  expansion  curve,  where  the  greatest  variation  takes  place  in  expansion, 
but  they  can  be  put  as  near  together  or  as  far  apart  as  the  demonstrator  may 
choose. 

Now,  from  the  intersection  of  the  ordinates,  3,  4,  5,  6,  7,  and  the  line  B, 
draw  the  radial  lines  from  the  point  K  to  each  separate  point  of  intersection. 
Now,  wherever  the  radial  lines  cross  the  line  G,  is  the  point  of  our  next 
computation.  From  the  points  of  the  radial  lines  crossing  the  ordinate  G,  we 
next  draw  lines  at  right  angles  to  G  until  they  cross  the  ordinates  3,  4,  5,  6,  7. 
We  have  here  then  following  out  this  process  with  each  one  of  the  lines  to 
their  crossing  with  G,  the  lines,  8,  9,  10,  11,  12,  13.  Now  wherever  these 
two  lines  8-3,  9-4,  10-5,  11-6,  12-7  intersect,  through  the  points  described  by 
their  intersection  lies  the  hyperbolic  curve  from  the  demonstration. 

In  this  case  it  will  be  noted,  to  return  to  the  diagram  for  a  moment,  that 
we  start  off  with  an  initial  pressure  of  70  pounds.  The  steam  pressure  is 
gradually  reduced  or,  as  engineers  term  it,  wire-drawn,  throttled  so  that  it  is 
constantly  reduced  in  pressure  on  the  diagram.  At  the  point  where  the 
ordinate  G  is  erected,  we  have  13  pounds  less  than  we  started  with,  or  57 
pounds  realized  at  that  point ;  dropping  off  still  further,  so  that  at  the  point 
where  D  intersects  the  hyperbolic  curve  we  have  only  49  pounds.  Now  with 
the  ordinary  demonstration  which  has  been  so  frequently  printed,  and  upon 
which  so  many  arguments  have  been  based,  in  this  diagram  we  should  have 
no  possible  data  with  any  sort  of  certainty,  for  ascertaining  precisely  where 
the  steam  was  cut  off.  In  this  case,  the  result  proved  the  correctness  of  the 
assumption,  and  the  assumption  is  based  on  the  fact  that  the  demonstration  is 
correct.  The  theoretical  curve  in  this  case  starts  from  the  point  B,  G,  and  strikes 
the  actual  line  of  the  instrument  at  the  point  I,  or  directly  over  the  line  D,  and 
the  two  lines,  which  are  very  clearly  drawn  (the  actual  line  of  the  indicator  in 
long  dots  and  the  theoretical  curve  very  fine  dots),  pass  over  each  other  for 
such  a  proportion  of  the  distance"  that  the  two  lines  are  inseparable  until 


TWENTY  YEARS  WITH  THE  INDICATOR.  145 

almost  the  commencement  of  exhaust.  At  the  last  ordinate  the  line  of  the 
instrument  is  very  slightly  above  the  theoretical  line.  The  line  D  may  be 
placed  anywhere  on  the  expansion  line  between  the  visible  point  of  cut-off 
and  the  visible  point  of  release  ; .  and  in  the  case  of  some  diagrams,  which  will 
be  shown  further  on,  it  will  be  seen  that  where  difficulty  exists,  in  every  one 
of  these  points  the  demonstration  proves  what  the  action  would  have  been  if 
there  is  any  accuracy  at  all  to  the  action  of  the  valves,  and  a  cut  off  was 
intended.  In  this  case  the  action  of  the  engine  was  fettered  somewhat  by  a 
late  release,  we  might  say,  but,  as  a  matter  of  fact,  while  the  exhaust  valve 
could  have  been  opened  a  trifle  earlier,  the  amount  of  steam  in  the  cylinder 
was  enormous,  and  the  exhaust  is  partially  clogged  for  that  reason.  It  will 
be  interesting  when  we  state  that  the  theoretical  use  of  steam  on  this  dia- 


FIG.  98. 

gram,  Fig.  98,  measuring  the  full  boiler  pressure  up  to  the  point  of  cut-off, 
then  following  the  theoretical  line,  making  a  perfect  exhaust,  is  792,  while  the 
actual  useful  effect  measured  by  the  planimeter  is  715,  giving  us  a  percentage 
of  a  trifle  over  90  per  cent.,  and  yet  this  is  by  no  means  good  practice  ;  it 
speaks  well  for  the  design  of  the  engine,  but  not  for  the  management  of  its 
owner. 

Kef  erring  to  the  demonstration  of  the  point  of  cut-off,  Fig,  98,  as  com- 
pared with  Figs.  96,  97,  shows  almost  the  other  extreme  of  the  efficiency  of 
the  application  of  this  demonstration  to  the  every-day  work  of  the  working 
engineer.  Any  engineer  with  a  steady  hand  can  do  all  that  we  have  been 
describing.  A  pair  of  steel  triangles,  we  prefer,  made  by  Brown  &  Sharpe, 
although  rubber  or  wood  will  do,  if  they  are  taken  care  of,  a  sharp  pencil, 
and  for  laying  out  the  theoretical  curve  a  series  of  curves  of  different  radius, 


£46  TWENTY  YEARS  WITH  THE  INDICATOR. 

which  can  be  bought  at  any  draughtsmen's  supply  place,  and  only  two  or 
three  will  be  required  for  a  very  large  range  of  work — this  is  all  the  appa- 
ratus— and  a  board  a  foot  square,  covered  with  blotting  paper  or  coarse  rope 
paper  not  sized  or  glazy  finished,  completes  the  whole  apparatus. 


LESSON  XLHI. 


THE  DEMONSTRATION  OF  THE  POINT  OF  CUT-OFF  AND  THE  LAYING  OUT 
OF  THE  THEORETICAL  CURVE  WITHOUT  REFERENCE  LETTERS. 

If  the  two  previous  lessons  have  been  carefully  studied,  the  reader  will 
have  a  pretty  good  idea  of  how  to  do,  and  what  is  being  attempted.  Fig.  99 
is  taken  from  the  steamer  City  of  Worcester,  Norwich  Line  of  New  York  and 
New  England  Steamers,  between  Boston  and  New  York.  The  diagram  illus- 


"    ,'  I 


**  s   r 

M  •"•      I 


I... 


/ 

/"'' 


.i---X-'--^... 


FIG.  99. 

trated  was  taken  while  her  engines  were  being  adjusted  and  before  they  were 
fairly  complete.  We  have  chosen  this  diagram  for  the  especial  purpose  of 
making  the  demonstration  upon  it,  not  having  taken  the  most  perfect  one  for 
that  purpose.  This  diagram  was  taken  while  she  was  at  full  speed,  her 
cylinders  being  90  inches  in  diameter,  12  feet  stroke,  35  pounds  pressure  by 
gauge,  22  inches  of  vacuum  per  gauge,  throttle  wide  open,  running  18  4-  rev- 
olutions per  minute,  24  scale. 


TWENTY  YEARS  WITH  THE  IN  DIG  A  TOR.  147 

The  bottom  diagram  in  this  case  carries  steam  the  greatest  distance,  as  is 
usual  in  marine  engines.  We  have  been  compelled  to  draw  our  line  repre- 
senting the  initial  pressure  a  very  trifle  above  the  actual,  in  order  to  allow  the 
lines  of  the  diagram  to  show,  for  the  bottom  end  of  the  cylinder,  although  it 
takes  steam  late  on  the  opening  of  the  valve.  In  this  case  it  realizes  full  boiler 
pressure  after  having  traveled  several  inches,  and  at  the  point  of  cut-off  by 
demonstration  loses  only  three  pounds  from  the  initial ;  while  the  top  end 
realizes  full  boiler  pressure  to  the  very  point  of  cut-off  visibly.  The  release 
as  shown  in  these  diagrams  is  rather  late,  later  diagrams  improved  it  very 
much  ;  so  the  vacuum  in  this  case  was  improved  after. 

The  base  line  in  this  case  is  erected  at  about  half-way  on  the  expansion 
line.  The  parallels  are  drawn  and  the  point  of  cut-off  located  very  closely  to 
what  we  would  have  termed  the  visible  point.  Radial  lines  and  ordinates  are 
erected  as  before  stated,  and  where  the  ordinate  and  the  line  from  the  point 
of  cut-off  cross,  it  will  be  found  to  almost  touch  in  each  of  the  four  cases,  the 
line  of  the  indicator  as  it  left  the  diagram,  so  nearly  at  least,  that  we  have 
not  thought  it  worth  while  to  attempt  to  draw  in  the  theoretical  line,  from 
the  fact  that  the  two  lines  are  so  very  close  together  that  it  would  lead  to 
a  confusion  in  the  mind  of  the  reader.  The  top  end  of  the  cylinder  is  a  little 
late  in  taking  steam  but  not  as  late  as  the  bottom  ;  the  result  of  this  is  shown 
in  the  slightly  increased  pressure  and  in  the  fact  that  the  steam  line  in  itself 
is  much  straighter  than  in  the  other  end. 

We  desire  it  understood  that  this  diagram  was  not  selected  to  show  the 
performance  of  the  steamer ;  it  was  selected  rather  as  a  diagram,  somewhat 
distorted,  for  the  sole  purpose  of  showing  that  the  demonstration  of  the 
point  of  cut-off  was  equally  as  applicable  to  a  diagram  in  which  the  lines  were 
not  clearly  established,  and  that  the  result  could  be  depended  upon  for  prac- 
tical application  aside  from  any  or  all  theoretical  questions. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


LESSON  XLIY. 


MODERN  STEAMSHIP  ENGINES    EXAMINED   BOTH   WITH  REFERENCE  TO 

ECONOMY  AND   THE  APPLICATION   OF   THE  DETERMINATION  OF 

THE  POINT  OF  CUT-OFF,  AS  WELL  AS  A  COMPARISON  OF  THE 

ACCURACY  OF  TWO  DIFFERENT  INDICATORS  ON  THE  SAME 

SHIP. 

Figs.  100  and  101  are  from  a  modern  steamship  running  between  New 

York  and .  The  diagrams  100  and  101  were  taken  with  an 

English  instrument  furnished  by  the  builders  of  the  vessel.  There  are  several 
very  noticeable  features  about  this  diagram  100.  The  bottom  end  of  the 
cylinder  gives  us  more  than  boiler  pressure ;  this  cannot  possibly  be,  the 
boiler  pressure  as  given  at  the  moment  was  78  pounds,  scale  32  ;  we  have 
fully  80  pounds  as  per  indicator  card.  The  steam  lines  are  very  irregular  and 
the  expansion  line,  it  will  be  noticed,  is  very  much  higher  than  it  should  be 
about  the  point  of  cut-off,  showing  first,  that  the  steam  is  throttled  in  the 
passage-ways,  and  next,  that  the  valve  closes  slowly  and  continues  to  admit 
steam.  The  stroke  of  the  engine  is  54  inches.  We  have  located  the  point,  of 
cut-off  from  the  usual  demonstration  and  it  will  be  noticed  that  the  curve  from 
the  release,  following  up  the  expansion  line,  denotes  where  the  steam  to  have 
been  cut  off,  would  have  given  the  theoretical  line  following  the  expansion 
the  majority  of  the  way. 

The  release  of  the  engine  appears  to  be  very  good,  and  it  is  at  38  pounds 
above  the  atmospheric  line,  but  there  is  something  very  curious  about  the 
exhausting  of  the  engine  from  either  end,  with  reference  to  the  positively 
straight  line  A,  B,  while  as  a  matter  of  fact  such  a  line  as  this,  where  the  re- 
ceiver is  used  as  between  the  high  and  low  pressure  cylinder,  cannot  be  made, 
if  we  are  to  have  any  faith  in  modern  engineering.  It  shows,  therefore,  that 
there  must  be  something  wrong  with  this  indicator,  and  if  we  come  to  analyze 
it  a  little  further  we  shall  probably  find  it.  By  the  indicator,  the  steam  valve 
closes  at  29f  inches  of  the  stroke  on  the  bottom  ;  this  gives  us  an  indicated 
horse-power  of  1255J.  The  exhaust  valve  closes  on  a  receiver  pressure  of  19 
pounds  at  four  inches  before  the  end  of  the  stroke,  while  on  the  top  end  the 
exhaust  valve  closes  at  5^fo  inches,  the  top  giving  1129  horse  power. 

If  we  compare  this  with  the  low  pressure,  Fig.  101,  the  line  B  represents 
the  pressure  of  steam  in  the  receiver,  while  the  line  A  represents  the  realized 
pressure  on  the  piston,  which  is  11  pounds,  while  the  receiver  pressure  is  19 
pounds.  We  have  made  the  demonstration  upon  the  top  end  showing  the 
cutting  off  at  26 J  inches  of  the  stroke,  giving  1293.72  horse-power,  while  the 
bottom  end  gives  1341.93  horse-power.  Only  about  half  the  receiver  pressure 


TWENTY  YEARS  WITH  THE  INDICATOR.  149 

is  realized,  that  is  carried  one-half  stroke  and  shows  a  very  fair  performance. 
The  vacuum  only  18  inches  is  realized  as  the  extreme,  giving  9  pounds. 

For  the  sake  of  comparison,  Figs.  102  and  103  are  given,  taken  from  the 
Improved  Thompson  indicator,  the  American  Steam  Gauge  Company's  build, 
from  the  same  ship,  arrangements  previously  being  made ;  these  followed  100 
and  101  as  soon  as  the  instruments  could  be  changed,  the  ship  running  under 
the  same  pressure  of  steam,  same  number  of  revolutions,  smooth  water. 
Here  we  have  a  decided  contrast.  Fig.  102  shows  the  high  pressure  cylinder, 
and  we  have  here  erected  three  different  curves.  A,  Fig.  102  is  the  theoretical 
curve  from  the  arrow-head  in  the  line  D,  which  shows  that  that  cylinder 
actually  used  steam  sufficient  to  cut  off  at  25-I5g-  inches,  giving  an  effective 
horse-power  of  988.2.  B  is  from  the  initial  pressure  78  pounds,  scale  40,  and 
shows  what  was  expected  of  the  engine,  while  C  is  the  theoretical  curve  from 
the  terminal  pressure  showing  quite  another  result.  The  line  B  shows  what 
was  expected,  viz.  :  to  cut  off  at  one-third  and  to  realize  boiler  pressure.  We 
find,  however,  the  terminal  pressure  of  the  diagram  is  27  pounds  above  the 
atmosphere,  while  the  terminal  pressure  of  the  curve  from  the  supposed 
point  was  20  pounds  above  the  atmosphere.  The  line  C  shows  the  engine  to 
have  cut  off  at  21^^-  inches  of  the  stroke,  if  the  terminal  pressure  was  right. 
It  will  be  seen  that  the  diagram  upon  which  the  two  curves  are  erected,  only 
realizes  70  pounds  of  steam,  and  that  at  one-third  stroke  12  pounds  less  than 
that  is  realized  on  the  piston  head.  The  line  A,  as  drawn  from  the  data  given, 
shows  about  the  actual  performance  of  the  engine  cutting-off  realized  press- 
ure at  25.7  inches,  developing  1075.73  horse-power.  The  dotted  line  E,  if 
continued,  would  barely  touch  the  end  of  each  diagram,  and  shows  the  rise 
in  pressure  in  the  receiver,  between  the  commencement  and  middle  of  the  ex- 
haust, amounting  in  this  case  to  about  7£  or  8  pounds.  The  minimum 
amount  of  pressure  in  the  receiver  in  this  case  is  9  pounds,  the  greatest 
amount  14 \  to  15^. 

Another  point  engineers  often  require  has  been  carefully  figured  on  the 
right-hand  diagram  where  B  and  C  are  shown,  the  exhaust  valve  of  the  high 
pressure  engine  closes  at  5.2+  inches  before  the  end  of  the  stroke,  while  on 
the  left  hand  diagram  the  exhaust  valve  closes  at  7.8  -I-  inches. 

Fig.  103,  scale  10,  realizes  a  trifle  over  ten  pounds  of  the  receiver  press- 
ure. In  this  case,  we  have  applied  the  demonstration  from  the  average  of 
the  expansion  line,  as  nearly  as  we  can  judge.  The  action  of  the  valves,  in 
this  case,  shows  plainly  the  change  in  pressure  in  the  receiver  from  the  com- 
mencement to  the  middle  of  the  exhaust.  The  steam  line  is  a  very  peculiar 
one,  and  the  demonstration  shows  that  the  valve  was  closed  at  21.7  inches  of 
the  stroke,  giving  a  horse-power  of  1042.4,  while  the  other  end  gives  1143.48 
horse-power.  There  are  one  or  two  points  with  reference  to  this  diagram 
worthy  of  notice.  On  the  left-hand  diagram  the  exhaust  valve  closes  at  11.85  -f 
inches  of  the  stroke,  at  a  lower  pressure  than  the  right-hand  end,  which  closes 
at  10.53  inches  of  the  stroke.  The  cushion  or  compression,  in  this  case, 
plainly  shows  that  the  higher  pressure  and  shorter  closure  produced  the 


150  TWENTY  YEARS  WITH  THE  INDICATOR. 

highest  compression.       The  vacuum  shows  a  trifle  over  ten  pounds  at  the 
highest,  the  lowest  being  eight. 

Diagrams  100  and  101  show  the  total  amount  of  power  required  to  drive 
the  ship  as  2510.09  horse-power,  while  102  and  103,  taken  within  a  very  few 
moments  of  the  others  and  as  near  as  possible  under  the  same  circumstances, 
show  the  probably  correct  action  of  the  valves,  and  the  correct  amount  of 
power  as  2124.94  horse-power.  102  shows  plainly  the  rise  in  the  receiver  or 
exhaust  line,  and  103  plainly  shows  this  action  in  the  steam  and  expansion 
line  of  the  right-hand  diagram.  Experiments  are  now  being  conducted  on 
that  ship  with  a  view  to  adjustment  and  finding  where  the  engines  will  do  the 
best  work.  We  would  not  attribute  any  motive,  but  it  is  somewhat  curious 
that  the  indicator  furnished  should  make  a  difference  of  a  few  hundred  horse- 
power in  the  power  required  to  drive  a  ship,  and,  therefore,  presumably  make 
the  amount  of  fuel  per  horse-power  less  than  if  the  actual  amount  of  power 
was  known  to  be  much  less  than  it  was  supposed,  and  the  amount  of  fuel 
much  more  than  it  had  been  considered.  These  diagrams  are  well  worthy  of 
a  careful  study  for  they  will  interest  stationary  engineers  as  much  as  marine. 
We  should  have  grave  doubts  as  to  the  economy  of  these  engines  as  compared 
with  some  of  the  examples  from  other  engines  which  will  follow. 


FIG.  100. 


TWENTY  YEARS  WITH  THE  INDICATOR.  151 


B 


FIG.  101. 


r- 


B 


FIG.  102. 


152  TWENTY  YEARS  WITH  THE  INDICATOR. 


FIG.  103. 


LESSON  XLY. 


3ADLY  THROTTLED  ENGINE,    LOSS   IN  INITIAL  PRESSURE,  ANI)  LOSS  IN 

VALVES. 

The  diagram  Fig.  104  is  from  an  engine  sixteen  inches  cylinder,  thirty- 
six  inches  stroke,  running  sixty  revolutions,   boiler  pressure   eighty  pounds, 


FIG.  104 


TWENTY  YEARS  WITH  THE  INDICATOR.  153 

scale  forty,  with  a  three-inch  feed  pipe  and  a  five-inch  exhaust  pipe.  There 
are  points  of  interest  about  this  diagram  well  worth  examination. 

A  represents  the  line  of  absolute  vacuum,  B  the  line  of  realized  pressure, 
C  boiler  pressure.  It  will  be  noted  there  is  a  wide  difference  between  the 
lines  B  C  ;  for  with  eighty  pounds  boiler  pressure,  there  is  only  62£  pounds 
initial  pressure,  the  steam  valve  opens  slowly,  and  we  doubt  if  it  ever  gets 
wide  open,  judging  from  the  steam  line.  From  the  diagram  there  is  nothing 
positive  to  tell  where  the  point  of  cut-off  is,  so  we  must  resort  to  the  demon- 
stration to  gain  information.  In  this  case  we  erect  the  line,  D,  rather  past  the 
center  of  the  expansion  line.  We  then  draw  the  first  parallel,  F,  from  the  in- 
tersection of  D  A  to  the  intersection  of  F  B.  The  line  E  is  then  drawn 
parallel  with  F  from  A  to  B.  Wherever  the  line  E  touches  B,  from  that  point 
drop  an  ordinate  G,  which  represents  virtually  the  volume  of  steam  admitted 
to  the  cylinder  to  do  the  work,  and  this  line  measures  the  amount  of  steam, 
from  the  commencement  of  the  stroke  to  its  cutting  off,  that  was  used  to  pro- 
duce the  known  pressure  at  D,  supposing  the  steam  had  been  properly 
put  into  the  cylinder  and  that  valves  and  piston  were  tight  so  that  it  was 
correctly  handled  after  it  was  once  put  there  ;  but,  unfortunately,  the  steam 
did  not  get  in  on  the  piston  as  it  should  have  done.  Now,  had  the  proper 
amount  of  steam  been  correctly  applied  between  the  introduction  and  the  line 
G,  it  would  have  followed  out  the  line  B  to  the  point  B  G,  and  then  would 
have  followed  the  theoretical  line  or  the  dotted  line.  But  in  the  first  place 
we  see  that  it  falls  away  short  of  the  theoretical  line  until  it  reaches  the  fourth 
ordinate  ;  at  that  point  it  seems  to  go  above  the  theoretical  line,  we  find  at 
the  ninth  ordinate  it  commences  to  exhaust  at  the  very  point  where  it  should 
have  expanded  to. 

To  refer  again  to  the  demonstration  and  its  purpose,  this  application  is 
not  at  all  to  raise  questions  to  confuse  the  engineers,  but  rather  to  show  them 
different  points  which  arise  in  our  own  practice  and  that  of  others,  where  so 
many  of  these  things  are  constantly  coming  up  which  vex  the  operator  and 
the  builder.  In  this  case  it  is  perfectly  fair  to  presume  that  the  stream  drifted 
in  after  the  valves  commenced  to  shut,  gradually  ran  down  on  the  line  G,  until 
the  expansion  is  five  pounds  at  the  first  ordinate  below  the  theoretical  line. 
This  theoretical  line  is  based  on  the  actual  pressure  of  steam  at  the  line  D, 
or  the  base  line,  so  that  the  pressure  at  the  first  ordinate  should  have  been 
five  pounds  more  than  it  is ;  at  the  second  ordinate  plus  three  pounds  more 
than  it  is ;  at  the  third  ordinate  two  pounds ;  at  the  fourth  ordinate  the  lines 
virtually  run  together  ;  at  the  fifth  ordinate  the  theoretical  line  runs  below 
the  line  of  the  instrument ;  at  the  sixth  ordinate  still  more  below ;  seventh, 
eighth,  and  ninth  increase  until  we  stop  at  the  ninth  ordinate  five  pounds 
above  the  line,  as  we  were  five  pounds  below  at  the  first,  while  the  distance 
from  the  base  line  D  to  the  ninth  ordinate  is  about  the  same  as  that  of  the 
ordinate  G. 

Now,  what  is  the  cause  of  this  almost  exact  balancing  of  the  figure  *?  Why 
has  it  been  below  in  one  point  and  above  in  the  other  ?  There  are  two  reasons 
that  could  make  it  so,  and  the  indicator  cannot  tell  us  which  of  the  two  it  was. 


154  TWENTY  YEARS  WITH  THE  INDICATOR. 

In  the  first  place  the  pressure  actually  was  below  what  it  should  have  been , 
in  the  last,  it  was  above.  Now,  this  pressure  may  have  been  caused  by  a 
leaking-by  of  the  piston  or  valves,  and  in  the  one  case  it  would  account  for 
the  terminal  pressure  at  the  ninth  ordinate,  probably  to  be  more  like  a  leak 
in  the  valves ;  or,  if  the  steam  was  wet,  there  might  be  a  certain  amount  of 
re-evaporation  which  would  tend  to  keep  the  pressure  a  little  above  its  theo- 
retical value  or  its  real  value.  This  shows  how  unfair  it  is  to  base  any  absolute 
demonstration  on  the  terminal  pressure,  as  showing  the  real  action  of  the 
engine.  If  the  piston  had  been  leaking-by  during  expansion  to  any  such  ex- 
tent, the  leak  would  have  shown  on  the  exhaust  of  the  other  side,  and  as  it 
did  not,  we  know  that  the  opening  of  the  valve  was  insufficient  from  the  drop- 
ping of  pressure  below  B  on  G  at  point  of  cut-off,  and  also  that  the  pressure 
at  B,  cut-off  at  G,  gives  us  the  volume  of  steam  to  give  the  pressure,  D,  at 
that  particular  point  in  the  expansion  line,  and  that  the  valve  was  slow  in 
closing,  or,  when  closed  allowed  steam  to  pass  through,  or,  leaked  sufficient 
steam  to  raise  the  terminal  pressure  as  shown,  wasting  the  62£  Ibs.  of  steam 
realized  in  the  cylinder  by  valves  insufficient  in  area  and  probably  insufficient 
in  their  relative  motion  to  give  steam  for  the  speed  of  the  piston  at  the  reg- 
ular speed  of  the  engine. 


LESSON  XLVI. 


HIGH-SPEED  ENGINE  DIAGRAM. 

The  diagram  Fig.  105,  in  this  lesson  was  taken  from  an  Armington  & 
Sims  engine,  8  J  inches  diameter,  ten  inches  stroke,  running  at  320  revolutions 
per  minute,  boiler  pressure  seventy,  Thompson  improved  indicator,  forty 
scale.  The  load  in  this  case  was  given  by  a  lever  bearing  upon  the  under 
side  of  the  balance  wheel,  and  in  several  instances  the  load  varied  by  intention 
from  the  mere  friction  of  the  engine  to  25  or  28  horse-power,  within  a  quarter 
of  a  minute.  At  the  particular  instant  when  this  diagram  was  taken,  the 
load  was  constant  for  the  sake  of  ascertaining  the  accuracy  of  the  indicator, 
and  this  was  only  one  of  several  diagrams  in  the  series,  and  this  particular 
diagram  is  chosen  in  order  to  show  the  largest  range  of  variation  recorded  ; 
in  other  words,  the  worst  diagram  of  the  set. 

The  admission  line  at  A  will  be  seen  to  vary  a  little  from  the  vertical  line, 
whereas  at  B  the  impact  given  by  the  admission  raises  the  pressure  some- 
what, and  at  the  same  time  is  a  trifle  late  as  compared  with  the  movement  of 
the  piston.  The  oscillations,  it  will  be  seen,  are  confined,  and  the  steam  line, 


TWENTY  YEARS  WITH  THE  INDICATOR. 


'55 


when  fully  drawn,  stands  at  sixty  pounds,  maintaining  fifty-seven  to  the  point 
of  cut-off  at  C.  It  is  a  curious  fact  that  some  makers  of  indicators  are  re- 
cently claiming  that  the  expansion  line  musj;  be  without  oscillations,  similar 
to  those  shown  in  this  diagram,  in  other  words,  their  instruments  draw  in  the 
hyperbolic  curve  perfectly.  In  this  case  we  wish  to  call  the  attention  of  our 
readers  to  the  fact  that  a  number  of  elements  are  at  work  between  the  points 
C  and  D,  in  order  to  prepare  them  to  reason  out  in  their  own  minds  as  to 
whether  our  own  ideas  upon  the  subject  will  bear  the  application  of  reasoning 
from  the  stand-point  of  fact. 

This  engine  is  traveling  very  fast ;  at  the  point  C  the  valve  is  closed  or 
very  nearly  so ;  every  thousandth  of  an  inch  that  the  piston  moves  forward 
on  its  stroke  increases  the  volume  of  the  cylinder  ;  no  more  steam  is  being 
admitted  ;  an  increase  of  volume  means  a  decrease  of  pressure ;  a  decrease  of 
pressure  means  a  decrease  of  temperature,  and  a  decrease  of  temperature 
means,  when  applied  to  steam,  an  increase  of  water  present  in  the  cylinder. 
Now  the  ratio  of  the  volume  of  the  cylinder  is  increasing  all  the  while  after 


FIG.  105. 

the  valve  closes  ;  the  volume  increases,  the  pressure  decreases,  the  water  in- 
creases, etc.  Now,  is  it  possible  for  steam — supposing  it  was  a  perfectly  dry 
steam  at  this  point,  which  it  is  not — is  it  possible  to  make  any  instrument 
that  will  make  any  portion  of  a  hyperbolic  curve  when  these  several  elements 
are  each  one  working  negatively  upon  the  other  ?  Even  after  the  release 
commences,  which  is  at  D,  it  will  be  found  then  that  the  variation  of  volume, 
temperature,  etc.,  make  a  still  further  fluctuation  in  the  line  at  E,  by  which 
time  the  exhaust  port  is  fully  open.  We  shall  show,  in  a  subsequent  lesson, 
that  it  is  not  precisely  the  correct  theory,  if  men  are  to  make  truthful  in- 
dicators. 

Now,  added  to  the  elements  that  we  have  cited,  there  is  another  very  im- 
portant one,  the  expansion  and  contraction  of  the  metal,  the  weight  of  the  pis- 
ton, change  in  the  spring,  the  friction  of  the  moving  parts,  which  is  but  ex- 
tremely little,  yet  it  is  something.  Perhaps  some  one  can  tell  us  how  it  is  pos- 
sible to  make  an  indicator  tell  an  untruth,  or  in  other  words,  make  some  portion 
of  the  hyperbolic  curve  from  C  to  D,  instead  of  the  undulating  line,  which  is 


156  TWENTY  YEARS  WITH  THE  INDICATOR, 

without  doubt  caused  by  the  various  elements  to  which  we  have  referred,  and 
it  is  somewhat  curious  that  when  the  exhaust  valve  closes  near  F,  in  the  com- 
pression of  the  steam,  the  increase  of  density  or  pressure  by  shutting  the 
steam  up  and  compressing  it  brings  back  certain  units  of  heat,  and  that  the 
compression  line  has  certainly,  in  the  same  ratio,  given  us  the  undulations  in 
.an  inverse  way,  (showing  compression)  to  what  the  expansion  line  from  C  to 
D  is.  Compare  the  lines  F  A  and  C  D,  and  tell  us  why  these  changes  should 
take  place,  one  proving  the  other.  It  will  be  noticed  that  the  undulations  in 
the  line  are  reversed  in  F  A  to  what  they  are  in  C  D,  showing  that  the  expan- 
sion with  the  indicator  piston  upon  the  steam  is  very  correctly  noted,  while 
on  the  other  side  in  compression  the  steam  is  driven  up  against  the  piston, 
showing  the  same  effect  precisely,  but  that  the  directions  of  the  lines  are  re- 
versed. 

The  diagram  shows  a  very  good  use  of  steam ;  possibly  the  action  of  the 
steam  valve  should  be  quickened  a  trifle  in  its  relation  to  the  piston  of  the 
engine,  that  would  make  a  somewhat  sharper  corner  at  the  termination  of  re- 
lease and  commencement  of  exhaust,  and  would  also  carry  the  compression  a 
trifle  higher  and  avoid  the  little  hook  at  A,  or  in  other  words,  would  run  the 
compression  line  into  the  steam  line  and  would  bring  the  point  B  nearer  the 
vertical  line  shown.  Taken  all  in  all,  it  is  a  beautiful  specimen  of  the  high- 
speed engine  diagram  as  well  as  of  the  indicator's  work.  The  three  lines,  as 
shown  in  the  original,  are  carefully  reproduced  in  all  their  variation,  and  the 
subject  of  the  maintenance  of  pressure,  quick  expansion,  almost  locomotive 
release,  as  well  as  locomotive  compression  are  well  executed  and  illustrated, 
but  with  the  full  effect  of  boiler  pressure  to  the  point  of  cut-off,  or  a  close  ap- 
proximation to  it,  and  a  fine  exhaust,  both  showing  that  boiler  pressure  and 
free  exhaust  can  be  realized  in  this  type  of  engine,  and  are  accomplished  in 
every-day  work. 


LESSON  XLYII. 


MEDIUM  HIGH  SPEED  ENGINE. 

Fig.  106  is  from  a  different  type  of  engine ,  one  of  medium  high  speed, 
which  has  not  been  running  many  months.  The  diagram  is  from  the  Buck- 
eye engine,  twenty-four  inches  diameter,  thirty-six  inches  stroke,  100  revolu- 
tions per  minute,  condensing,  one  of  a  pair,  front  end  of  the  left  hand. 
Boiler  pressure  seventy-two,  scale  thirty,  Thompson  improved  indicator. 

Some  pains  have  been  taken  to  make  the  demonstration  as  plain  as  pos- 


TWENTY  YEARS  WITH  THE  INDICA  TOE. 


T57 


sible  in  this  case,  for  those  not  familiar  with  the  new  method  of  laying  out  the 
point  of  cut-off,  and  then  applying  the  theoretical  curve  for  efficiency,  or  to 
detect  leakages  or  other  troubles. 


FIG.  106. 

On  this  diagram,  1  represents  the  absolute  vacuum,  2  the  atmospheric 
line  of  the  instrument,  3  the  line  of  realized  pressure  in  the  cylinder,  which 
is  sixty-eight  pounds  plus,  or  a  little  less  than  four  pounds  below  that  of 
boiler  pressure  at  the  instant  of  taking.  B  is  our  base  line  from  which  the 
whole  demonstration  is  made  with  reference  to  the  point  of  cut-off;  B  is  drawn 
from  a  point  a  little  to  the  left  of  the  center  of  the  line  of  expansion,  from 
that  to  the  line  of  absolute  vacuum.  From  the  intersection  of  the  lines  B,  1, 
the  line  D  is  drawn  to  the  intersection  of  3,  F,  representing  respectively  the 
realized  pressure  in  the  cylinder,  the  line  3,  and  F,  the  admission  line.  In 
this  case  we  do  not  know  what  the  clearance  is,  so  we  have  assumed  nothing, 
but  that  the  indicator  made  exactly  the  lines  showing  the  work  done,  so  that 
no  clearance  is  included.  We  show  the  steam  used,  and  as  we  do  not  know 
what  the  clearance  is,  we  prefer  to  call  it  an  unknown  quantity. 

C  is  drawn  parallel  to  D  exactly,  starting  from  1  and  crossing  the  end  of 
B  at  its  intersection  of  the  expansion  line.  Wherever  this  line  C  strikes  on 
3,  that  is  the  mechanical  point  of  cut-off,  assuming  only  that  geometry  is  cor- 
rect in  its  application,  wherever  the  intersection  of  C,  3,  comes,  there  is  the 
point  of  cut-off,  which  in  this  case  is  perceptibly  a  trifle  longer  by  the  instru- 
ment than  by  the  demonstration ;  we  do  not  believe  in  the  system  of  ordinates 
or  logarithms  where  pressure  and  temperature  are  combined,  but  we  believe 
if  a  mechanical  demonstration  is  capable  in  any  one  direction,  that  a  mechani- 
cal demonstration  is  far  better  for  us  to  locate  our  point  of  cut-off,  and  not 


158  TWENTY  YEARS  WITH  THE  INDICATOR. 

be  guessing,  supposing,  assuming,  etc.,  etc.;  hence  we  make  the  whole  of  our 
demonstration  mechanical  rather  than  by  assumption. 

We  have,  therefore,  the  intersection  G,  our  first  ordinate  with  the  line  3, 
is  the  actual  point  of  cut-off  from  that  part  of  the  expansion  line  where  we 
have  located  the  line  B,  from  the  point  A  all  these  lines  radiate.  (See  Lesson 
XLII  in  both  demonstrations.) 

We  locate  the  point  of  cut-off  mechanically,  and  then  demonstrate  the 
theoretical  curve  mechanically,  so  that  we  notice  here  a  variation  of  far  less 
than  the  width  of  the  line,  it  shows  us  clearly  that  the  valves  of  this  engine 
must  have  been  working  very  nearly  tight.  Practically  they  are  tight,  and 
wherever  any  broad  variation  from  the  actual  line  of  the  theoretical  curve 
from  the  point  of  cut-off  with  this  demonstration  occurs,  you  may  commence 
at  once  to  look  for  leaky  valves,  piston  rings  or  something  of  that  sort,  in 
this  case  it  means  nothing  ;  we  are  without  the  clearance  line,  and  this  dia- 
gram, as  it  stands,  is  simply  and  purely  an  actual  exponent  of  the  work  being 
done  at  the  time,  but  it  does  not  show  the  whole  bulk  of  the  steam  used,  only 
ae  we  know  precisely  what  the  clearance  of  that  end  of  the  engine  was,  but 
for  all  practical  purposes  we  would  not  give  a  farthing  to  know,  and  it  may 
be  well  to  say  here  that  the  clearance,  if  known,  would  add  its  volume  to 
steam  used,  but  would  in  no  way  affect  the  cut  off,  or  expansion.  We  have  a 
diagram  here  which  shows  a  very  fine  working  of  steam,  so  far  as  taking,  car- 
rying, cut-off,  expansion  and  release  go.  The  vacuum  might,  perhaps,  be  im- 
proved in  amount,  but  as  it  is  an  independent  condenser  and  no  part  of  the 
engine,  we  do  not  criticise  it.  It  starts  with  only  four  pounds,  runs  down  to 
nine,  ten,  eleven,  then  commences  to  go  the  other  way,  making  a  fine  com- 
pression, though  possibly  a  trifling  steam  lead. 

One  point  must  be  taken  care  of  in  locating  this  basis  for  the  demonstra- 
tion, and  that  is,  that  the  ordinate  B  should  never  be  drawn  too  early  in  the 
expansion  line,  for  steam,  like  any  other  body  where  work  is  being  done,  as 
a  steamship  or  a  train  of  cars,  takes  a  little  time  for  the  engine  to  get  to  pull- 
ing, and  so  it  takes  a  little  time  for  the  steam  to  settle  down  to  its  expansive 
work,  and  that  place  which  is  fair  for  it,  all  things  considered,  is  a  trifle 
beyond  the  center  or  when  the  speed  of  the  piston  is  very  slightly  diminished 
by  getting  up  on  the  crank ;  in  other  words,  where  the  speed  of  the  piston  is 
very  slightly  slower  and  the  pressure  of  steam  has  very  considerably  dimin- 
ished ;  sometimes  sudden  fluctuations  will  be  found  in  expansion  line  by 
rings  leaky,  in  such  a  case  get  two  or  three  points  and  demonstrate  from 
each,  and  so  find  where  the  leakage  occurs 


TWENTY  YE  ARK  WITH  THE  INDICATOR. 


T59 


LESSON  XLVIII. 


EXPENSIVE   USE  OF  STEAM.     COMPARISON  BETWEEN  EXHIBITED    FACT 

AND  POSSIBILITY. 


FIG.  107. 

In  Fig.  107  we  have  something  not  only  to  think  of,  but  something 
which  we  can  compare  as  between  the  application  of  geometry  to  fact  and 
mathematical  rendering  of  the  geometrical  delineation,  by  so  simple  a  process 
that  every  reader  who  has  a  planimeter  can,  in  fifteen  minutes,  tell  whether 
our  statements  are  correct  or  not.  We  have  chosen  about  as  awkward  a  dia- 
gram as  we  could  conveniently,  for  two  reasons :  almost  anybody  who  has 
been  reading  our  indicator  articles  for  the  past  few  years,  can  make  a  demon- 
stration on  a  finely-outlined  indicator  card ;  and  we  have  chosen  this  curiosity 
more  for  the  sake  of  the  application  of  our  own  method  of  finding  out,  first, 
where  the  steam  was  cut  off,  and  then  finding  out  what  ought  to  have  been 
done.  A  represents  the  line  of  boiler  pressure,  which  is  far  above  the  real- 
ized pressure  in  the  cylinder ;  B  represents  the  atmospheric  line  of  the  instru- 
ment ;  C  represents  absolute  vacuum  from  which  all  computations  are  made 
both  for  geometrical  demonstration  of  the  point  of  cut-off,  and  quite  another 
demonstration  having  nothing  to  do  with  the  first,  which  gives  us  the  theo- 
retical curve,  supposing  steam  does  expand  either  according  to  Mariotte's 
law  or  Kankine's  formulas ;  but  the  two  demonstrations  are  not  in  any  way 
connected,  beyond  that  the  line  D  shows  the  amount  of  steam  used  in  the  cyl- 
inder, the  volume  from  C  to  D  being  filled,  if  cut  off  and  properly  expanded, 
and  the  intersection  of  line  D  with  the  line  F  shows  point  of  cut-off  on  the 


160  TWENTY  YEARS  WITH  THE  INDICATOR. 

line  F.  The  engine  from  which  this  was  taken  was  running  eighty-two  revo- 
lutions per  minute,  scale  thirty,  governed  by  one  of  the  throttle  governors 
and  was  supposed  to  be  doing  good  work.  The  card  made  by  the  indicator 
starts  off  with  forty-five  pounds  initial  pressure,  makes  a  nice  little  jog  at  1, 
runs  along  at  forty-five  pounds,  and  commences  a  peculiar  gyration  at  2, 
dropping  off  suddenly  from  this  point  to  3,  rising  again  to  4,  and  making  a 
peculiar  short  curve,  commencing  at  5  again  to  run  in  a  straight  line,  and  at 
6  another  peculiar  vibration.  The  terminal  pressure  at  7  is  forty-one  pounds. 
We  have  thus  a  very  peculiar  expansion  line,  and  almost  any  one  with  any 
knowledge  of  steam  enginery  would  pronounce  it  not  by  any  means  a  model 
card,  but  we  have  less  to  do  with  this  than  with  the  next  factor  in  this  most 
interesting  case.  A  little  beyond  7  the  exhaust  valve  commences  to  open 
and  opens  slowly,  so  that  at  8  we  have  twenty-four  pounds  back  pressure,  at 
9  we  have  seventeen  pounds  and  at  10  ten  pounds.  The  back  pressure 
gradually  becomes  less  until  the  exhaust  valve  closes  at  11,  where  it  lias 
been  reduced  to  five  pounds  ;  we  have  all  the  space  bounded  between  the 
exhaust  line  of  the  instrument  and  the  atmospheric  line  of  the  instrument  B, 
making  a  large  area,  the  exhaust  being,  perhaps,  a  little  less  ragged  than  the 
upper  line  1  to  7.  The  closing  of  the  exhaust  valve  at  11  is  very  nearly  cor- 
rect, but  the  opening  from  and  after  7  shows  distinctly  that  the  motion  of 
the  valve  is  incorrect,  for  it  is  entirely  too  slow,  if  large  enough,  in  its  pro- 
portion to  the  stroke,  and  all  the  area  when  open  is  not  sufficient ;  hence  we 
do  not  realize  the  theoretical  line  of  exhaust,  nor  indeed  the  usual  exhaust  of 
a  half  pound  of  back  pressure.  The  planimeter  reading  of  the  indicator  card 
precisely  as  it  comes  from  the  instrument  is  473 ;  the  planimeter  reading  of 
the  area  covered  in  by  the  back  pressure  is  144  ;  then  we  have  an  area  of 
473  +  144=617.  Now  there  are  parties  in  the  world  who  claim  (we  will  call 
this  horse-power)  that  in  this  case  the  473  horse-power  is  transmitted  to  the 
machinery,  and  that  the  144  amounts  to  nothing.  Perhaps  this  is  so.  All 
engineers  know  that  the  boiler  capacity  is  invariably  measured  from  the 
atmospheric  line,  and  in  this  case  the  boiler  would  receive  credit  for  and 
would  actually  be  doing  617  horse-power.  It  is  claimed  also  that  the  back 
pressure  upon  one  end  equalizes  the  back  pressure  on  the  other ;  perhaps 
this  is  so ;  possibly  not.  Now,  while  the  piston  moves  from  1  to  7,  the  steam 
is  escaping  from  the  other  side  of  the  piston,  and  from  7  to  11  is  going  on,  on 
the  other  side  of  the  piston.  Now,  if  we  have  473  on  one  side  of  the  piston, 
144  added  to  it,  if  it  were  working  as  it  should,  but,  in  this  case,  working 
against  it,  does  it  require  anything  on  the  other  side  of  the  piston  to  push 
that  144  out  of  one  side  of  the  piston  and  out  of  one  end  of  the  cylinder, 
while  the  steam  is  making  the  card  upon  the  side  of  the  piston  in  the  direction 
of  from  1  to  7  ?  Now,  if  this  statement  is  a  fallacy  will  somebody  show  us 
where  ?  In  other  words  we  have  drawn  the  line  E  from  the  expansion  line  or 
steam  line,  whatever  it  may  be,  to  the  line  C ;  from  the  base  of  E  we  have 
drawn  a  line  to  the  intersection  of  F  G,  namely,  realized  pressure,  and  the 
boundary  line  of  the  card,  giving  the  steam  and  vacuum  lines,  parallels  to  this 
line,  which  is  omitted  in  the  engraving.  We  have  drawn  from  a  point  on  O  to 


TWENTY  YEARS  WITH  THE  INDICATOR.  i6z 

the  line  F,  which  crosses  the  line  F  at  the  intersection  of  D  F;  from  this  point 
we  drop  the  line  D.  Now,  the  space  bounded  by  the  line  C  G  F  D  represents 
the  volume  of  the  cylinder  at  which  steam  should  have  been  cut  off  in  order 
to  produce  its  equivalent  at  E.  Then  by  the  same  plan  given  in  Lesson  XLII, 
we  draw  in  a  theoretical  line  F.  Now,  we  assume  here  simply  that  had  the 
engine  been  handled  as  an  engine  should  have  been,  it  had  a  pound  or  so 
above  the  actual  initial  pressure,  that  it  would  have  been  cut  off  at  D  on  the 
line  F,  and  then  if  the  valves  were  tight  it  would  have  expanded  according  to 
the  curve  F,  and  if  it  had  exhausted  as  it  should  have  done,  it  would  have  re- 
turned upon  the  line  B.  There  is  something  curious  about  all  this.  The 
dotted  steam  and  expansion  line  with  the  correct  exhaust  gives  us  precisely 
the  same  planimeter  reading  as  in  the  diagram  above  473  without  the  144 
back  pressure.  This  may  be  the  correct  way  of  working  engines,  we  mean 
the  actual  diagram,  but  in  our  own  demonstration  we  have  only  shown  what 
the  engine  should  have  done,  providing  the  steam  were  worked  correctly  and 
at  the  real  boiler  pressure  instead  of  that  which  was  realized.  It  is  a  little 
curious  that  this  result  conies  out  precisely  as  it  does,  without  any  calcula- 
tion other  than  that  all  the  simple  demonstration  and  the  addition  of  about 
one-third  of  an  inch  in  length  for  clearance.  The  comparison  shows  a  most 
expensive  mis-application  of  steam. 


LESSON  XLIX. 


A  HIGH  SPEED  ENGINE,  RUN  AT  A  LARGELY  INCREASED  SPEED  TO  TRY 
AN  EXPERIMENT  WITH  THE  THOMPSON  IMPROVED  INDICATOR. 

The  author  was  among  the  very  first  of  the  engineers  who  had  actual  ex- 
perience with  the  high-speed  type  of  engines,  beginning  with  Mr.  Porter's 
engine  in  1869,  and  has  had  much  to  do  with  and  has  advocated  the  high 
speed  for  certain  purposes,  and  it  would  seem,  perhaps,  better  if  we  were  to 
give  some  few  illustrations  which  have  not  been  previously  given.  In  Fig.  108 
we  give  something  which  we  believe  never  before  done,  and  in  this  case  was 
done  for  an  experiment,  but  we  presume  will  soon  be  adopted  as  practice. 
It  is  a  well  known  fact  that  in  electric  lighting  long-stroke  engines  have  in 
some  cases  proved  to  be  (even  with  the  best  regulation)  very  undesirable, 
from  the  fact  that  on  the  incandescent  light  the  strokes  of  the  engine  can  be 
counted  with  the  utmost  precision,  if  any  one  will  give  careful  attention  to  it. 
On  the  other  hand,  with  some  high-speed  engines  the  short  stroke  has  been  a 


162 


TWENTY  YEARS  WITH  THE  IWJLU'CATOIt. 


disadvantage,  by  means  of  not  thoroughly  overcoming  what  was  expected  in 
the  matter  of  measurement  of  time  as  between  the  long  and  stort  stroke,  and 
the  high-speed  engine  requires  a  great  increase  of  accuracy,  if  such  a  thing  is 

i 


FIG.  108. 

possible,  over  the  slow  speed,  in  proportion  as  the  stroke  is  shorter,  than  the 
slow-speed  engine.  The  same  factor  of  an  increase  of  speed  from  the  com- 
mencement to  the  middle  of  the  stroke,  and  the  decrease  of  speed  from  the 
middle  to  the  end  of  the  stroke,  is  present  in  the  short-stroke  engine,  but  it 
becomes  beautifully  less  in  percentage  as  the  stroke  is  shortened  and  made 
more  frequent.  Tn  other  words,  the  visible  effect  on  a  high-speed  engine,  if 
run  at  regular  speed,  is  exceedingly  little.  Regular  speed  does  not  mean  a 
great  variation,  but  a  close  approximation  to  a  certain  line,  and  any  varia- 
tion from  this  is  very  noticeable  indeed,  and  is  not  only  noticeable,  but  has  a 
very  pernicious  effect  upon  the  film  of  the  incandescent  lamps. 

The  author  was  called  upon  to  make  a  test  with  some  indicators.  He 
had  desired  very  much  to  obtain  an  indicator  that  would  give  a  reliable  card 
from  an  engine  running  500  revolutions.  We  had  no  engine  ininning  500,  nor 
could  we  get  access  to  one,  but  through  the  courtesy  of  the  owner  of  an 
engine  we  were  allowed  access  to  his  engine  during  the  noon  hour,  with  the 
privilege  of  miming  it  into  the  afternoon  if  we  would  agree  to  stay  by  and 
take  care  of  it.  The  regular  speed  of  the  engine  was  a  little  above  300  per 
minute. 

We  set  the  regulator  arm-springs  down  as  much  as  we  dared  to,  adjusted 
our  indicators  as  nearly  as  possible,  and  opened  the  throttle  valve.  We  had 
intended  to  run  at  about  400,  but  were  simply  guessing  at  the  tension  of  the 
springs.  The  speed  was  simply  terrific  ;  counting  was  entirely  out  of  order, 


TWENTY  YEARS  WITH  THE  INDICATOR.  163 

and  the  engine  ran  as  smoothly  as  at  320.  Finally  the  gentleman  who  had 
invented  the  500-revolution-per-minute  engine  decided  that  he  would  experi- 
ment somewhere  in  the  neighborhood  of  the  speed  we  were  using.  A  counter 
was  then  procured,  and  we  found  that  our  speed  ran  in  fifteen  seconds  109, 
thirty  seconds  217,  one  minute  435,  and  two  minutes  gave  us  866.872  and 
870.  The  steam  was  then  let  into  one  of  our  new  Thompson  improved  in- 
dicators. Fig.  108  is  one  of  the  diagrams  taken  from  the  head  end  of  an 
Armington  &  Sims  engine,  8Jx  10,  435  revolutions,  boiler  pressure  90,  scale 
40.  A  represents  the  line  of  boiler  pressure  88  or  initial  pressure,  C  the  ver- 
tical line  at  right  angles  to  D,  which  is  the  atmospheric  line  of  the  instrument, 
and  E  the  line  of  absolute  vacuum.  In  this  case  the  line  of  the  diagram  above 
C,  where  the  compression  closes  and  the  steam  valve  opens,  shows  that  the 
steam  valve  is  slightly  in  advance  ;  in  other  words,  that  there  is  a  little  actual 
lead.  The  opening  of  this  valve  is  instant,  and  the  steam  in  this  particular 
case  shows  an  impact  rising  of  between  thirteen  and  fourteen  pounds,  but  it 
as  instantly  descends  to  about  four  pounds  below  realized  pressure.  The 
steam  line  is  then  carried  off  very  handsomely,  and  the  visible  point  of  cut-off 
is,  we  think,  for  such  a  speed,  very  plainly  shown. 

Here  comes  up  the  old  question  of  what  makes  a  wavy  line  of  expansion, 
and  we  do  not  think  we  have  far  to  seek  in  this  for  the  reason.  In  this  dia- 
gram there  is  no  assumption,  for  we  have  all  the  facts,  and  the  expansion  line, 
as  is  shown  in  the  first  dropping  after  the  cut-off  valve  has  closed,  descends 
something  below  the  theoretical,  then  rises  slightly  above,  again  falls  slightly 
below,  and  just  before  the  exhaust  valve  opens  at  J,  the  theoretic  and  the 
practical  line  in  its  oscillations  cross  each  other  absolutely.  The  sudden  out- 
let from  J  to  K  shows  us  that  the  steam  will  expand  in  any  thing  but  a  section 
of  a  hyperbolic  curve,  when  allowed  free  egress.  At  K  we  have  another  little 
oscillation,  another  sharp  curve  approximating  much  nearer  to  a  right  angle 
with  the  theoretic  curve,  and  at  L  we  have  still  another  oscillation.  The  cause 
of  this  we  have  frequently  been  asked  for,  and  lately  in  a  case  where  the  same 
factor  appeared.  Our  reasoning  of  this  is  :  From  J  to  K,  when  the  exhaust 
valve  opens,  there  is  a  sudden  exit  of  a  considerable  volume  of  steam  under  a 
pressure  of  thirty-three  pounds  above  the  atmosphere.  The  exhaust  pipe  in 
this  case  is  of  quite  a  length  and  when  the  steam  from  the  cylinder,  released 
by  the  exhaust  valve,  impinges  upon  the  steam  already  moving  in  the  exhaust 
pipe,  a  little  reaction  is  caused  by  this  very  elastic  medium,  which  makes  a 
crook  in  the  line  at  K.  The  steam  then  moves  along  again,  that  which  is 
being  released  from  the  cylinder  striking  or  pushing  the  other,  all  of  which 
is  very  elastic,  and  at  L  the  pressure  is  reduced  so  materially  that  no  further 
vibration  in  the  movement  of  the  body  of  steam  can  be  recorded  by  the  in- 
dicator ;  and  this  may  be  further  proved,  perhaps,  by  the  dropping  off  of  the 
line  as  it  turns  from  the  termination  of  the  exhaust  just  below  the  letter  L, 
dropping  down  nearly  two  pounds  before  the  exhaust  line  starts  on  its  con- 
tinuation. The  line  then,  it  will  be  noticed,  drops  a  little  as  the  exhaust  is 
completed  and  before  the  exhaust  valve  closes  again,  a  little  to  the  left  of  D. 
Here  we  have  precisely  these  same  vibrations  or  oscillations  or  changes  as  the 


164  TWENTY  YEARS  WITH  THE  INDICATOR. 

compression  increases,  showing  plainly  that  the  exhaust  valve  closes  and  the 
compression  ceases  in  amount  of  pounds,  making  a  nearly  straight  line  on  the 
upper  step  before  the  steam  valve  opens. 

Proceeding  with  our  usual  demonstration,  first  to  find  the  point  of  cut- 
off and  the  actual  amount  of  steam  used,  we  have  erected  here  the  line  F,  and, 
if  the  reader  will  notice,  we  have  erected  it  not  at  the  point  of  lowest  pressure, 
but  at  about  the  highest  point  after  the  expansion  really  gets  settled.  From 
F  we  carry  the  parallels  Gr  H,  and  in  this  case  we  have  included  the  actual 
measure  of  clearance  of  the  engine,  embracing  the  inside  of  the  valve,  the 
passage  from  the  valve  into  the  cylinder  and  the  actual  space  between  the 
piston  and  cylinder  head,  from  data  obtained  from  the  engine  when  still 
and  the  clearance  filled  with  water.  We  have  therefore  drawn  G  from  the 
intersection  of  F  E  to  the  intersection  of  A,  line  of  boiler  pressure,  B  repre- 
senting between  C  and  B  the  actual  amount  of  clearance  as  compared  with 
the  total  cubic  contents  of  the  cylinder  through  which  the  piston  moves.  In 
this  case  it  will  be  noticed  we  charge  the  engine  with  the  absolute  boiler 
pressure  ;  we  also  charge  it  with  every  particle  of  clearance  at  that  end  of  the 
cylinder. 

Having  thus  defined  the  point  of  cut-off,  we  draw  the  first  ordinate  from  A 
to  angle  formed  by  E  B,  see  lesson  XLII,  starting  from  the  intersection  of  the 
lines  B  E,  and  we  have  made  the  whole  demonstration  except  the  point  from 
which  the  lines  radiate,  and  these  are  omitted  purposely  in  order  to  show 
clearly  just  what  the  effect  of  the  action  is  ;  from  the  joining  of  the  second 
ordinate  with  a  line  at  right  angles  to  the  first  ordinate  at  the  crossing,  and 
the  process  being  repeated  by  the  third,  fourth,  fifth  and  sixth  ordinates 
through  these  points  from  the  first  ordinate  the  theoretical  curve  is  dotted. 
[t  will  be  noticed  that  the  second  ordinate  of  the  theoretical  curve  crosses  a 
trifle  above  the  actual  line  of  the  instrument,  and  at  about  the  center  of  the 
/stroke  or  when  the  speed  is  at  its  very  highest.  The  third  ordinate  crossing 
is  a  trifle  above  the  line  of  the  instrument,  the  fourth  is  a  trifle  below,  the  fifth 
is  absolutely  on  the  line. 

At  J  the  exhaust  valve  opens  and  the  curve  is  carried  forward,  passing  I, 
in  order  to  show  where  it  would  have  come  had  the  pressure  been  maintained 
by  keeping  the  exhaust  valve  closed.  We  have  not  figured  this  for  absolute 
effective  percentage,  though  the  percentage  is  very  high,  but  present  it  as  an 
example  from  actual  practice,  showing  that  we  may  charge  the  engine  with  its 
whole  clearance,  about  nine  per  cent.,  remembering  that  the  cylinder  is  8J 
inches  in  diameter,  and  that  while  the  clearance  may  be  large  in  proportion, 
the  handling  of  the  steam,  charging  everything  to  the  engine  that  we  may 
properly  or  justly  do,  is  most  excellent,  even  at  this  tremendous  speed.  It  is 
impossible  at  such  a  speed  as  this  to  take  a  card  quite  so  neatly  as  we  like  to 
do  from  one  running  80  to  125  per  minute,  for  if  you  touch  the  paper  at  all 
you  must  necessarily  make  several  records.  In  £his  case  the  lines  did  not 
vary  the  width  of  one  another  apart  at  any  point  of  the  diagram,  so  that  we 
have  engraved  a  single  line. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


165 


The  question  of  the  recording  of  the  lines  of  expansion  of  steam  under  press- 
are  and  the  oscillations  is,  to  our  own  mind,  always  an  evidence  of  extreme 
sensitiveness  and  reliability  in  the  indicator,  and  we  believe  that,  sooner  or 
later,  the  real  doctrine  of  the  expansion  of  steam  will  be  settled  upon  a  basis 
that  will  not  be  filled  with  vagaries. 


LESSON  L. 


CARRYING  STEAM  FULL  STROKE  AND  EXHAUSTING  UNDER   EXCESSIVE 

BACK  PRESSURE. 

In  Fig.  109  we  have  a  comparison  of  high  pressure  steam,  throttled  down 
and  then  carried  full  stroke,  and,  to  make  the  matter  all  the  worse,  the  exhaust 
is  nearly  equal  in  resistance  to  the  whole  amount  of  work  transmitted.  We 
have  made  some  comparisons  on  this  diagram,  both  from  the  boiler  pressure 
and  the  realized  pressure,  and  to  show  how  the  effective  use  of  the  steam  is 
entirely  done  away  with  and  no  economy  attained.  Boiler  pressure,  100  Ibs. ; 
revolutions,  114  per  minute  ;  scale,  60. 


FIG.  109. 

The  line  A  in  this  case  is  the  base  of  the  first  combination,  B  the  line  of 
boiler  pressure,  C  the  atmospheric  line  of  the  instrument,  D  the  absolute 
vacuum.  From  the  intersection  of  A  D,  we  draw  a  line  (according  to  our 
method  of  delineation)  to  the  intersection  of  I  B,  then  on  D  we  lay  off 


i66  TWENTY  YEARS  WITH  THE  INDICATOR. 

towards  J  the  sanie  distance  that  exists  between  the  intersection  of  A  and  the 
steam  line  of  the  indicator  card  and  the  line  D  I.  From  this  point  on  the 
line  D  we  find  the  point  through  the  top  of  the  line  A  which  intersects  B, 
from  which  we  drop  F,  showing  the  amount  of  steam  used  in  the  cylinder  to 
make  the  theoretical  expansion  curve  G,  showing  the  amount  of  steam  at  100 
pounds  cut-off  to  make  very  nearly  the  same  amount  of  work  as  that  shown 
by  the  indicator  diagram  and  the  back  pressure  ;  the  planimeter  reading  of 
the  indicator  diagram  outline  is  219,  the  back  pressure  194,  the  sum  of  the 
two  being  413,  while  if  we  take  100  pounds  of  steam,  cutting  it  off  so  that  A 
shall  equal  the  pressure  at  that  portion  of  the  stroke,  we  obtain  459.  Now 
there  is  a  point  here  to  be  considered ;  if  we  were  to  make  the  outline  bounded 
by  cutting  off  the  hundred  pounds  at  B  F,  taking  in  the  theoretical  curve  G, 
we  have  459  on  the  planimeter.  Now,  if  we  should  make  the  same  misuse  of 
steam  by  the  valve  in  the  larger  feature,  or  by  cutting  steam  off  in  admitting 
steam,  that  the  indicator  card  itself  makes  from  K  to  L,  the  sum  total  of  our 
areas  should  be  exact.  In  the  case  of  cutting  off  the  100  pounds  of  steam,  we 
have  simply  assumed  that  the  cylinder  is  to  be  filled  at  the  commencement  of 
the  stroke ;  so  that  while  with  100  pounds  of  steam,  cut-off  B  F  making  G,  re- 
turning on  C  and  admitting  again  on  the  line  I,  we  have  almost  a  perfectly 
theoretical  diagram ;  but  in  the  actual  misuse  and  abuse  of  steam  bounded 
by  the  dotted  line,  which  is  the  indicator  card,  we  have  219,  the  back  press- 
ure which  should  have  been  useful  effect,  and  the  little  triangle  bounded  by 
the  dotted  line  which  is  the  induction  pressure,  or  realized  pressure  after  the 
steam  valve  gets  open,  the  vertical  line  I  and  the  irregular  hypothenuse  K  L, 
we  have  an  area  of  26  on  the  planimeter,  hence  we  have  219  4- 194  4-  26  —  439 
as  against  459  developed  by  the  proper  use  of  steam. 

But  there  is  another  factor  in  the  case  :  Using  A  in  the  third  computa- 
tion as  our  base  line,  triangulating  with  the  dotted  line  E,  which  is  the  line 
of  realized  pressure  in  the  cylinder,  we  obtain  the  line  H  as  the  volume  of 
steam  admitted  at  that  pressure,  and  the  expansion  line  should  follow  the 
lower  line  M,  which  strikes  the  theoretical  curve  G  at  N,  and  then  follows  so 
near  that  it  is  almost  impossible  to  show  the  two  lines  on  the  card  ;  this  is 
supposed  to  exhaust  freely,  or  what  the  engine  should  have  done  had  the 
steam  been  entered  at  the  pressure  E,  at  the  very  commencement  of  the 
stroke,  cut  off  at  H,  expanded  on  M  G  to  the  terminal  pressure  and  exhausted 
freely.  In  this  case  we  have  352. 

By  this  time  our  readers  may  wish  to  know  what  all  these  letters,  figures 
and  lines  mean,  or  where  the  working  engineer  is  going  to  learn  anything 
from  such  a  mass  of  references.  Let  us  see  ;  in  the  first  place  we  had  a  hun- 
dred pounds  of  steam,  for  the  scale  is  60,  the  engine  was  running  114  revo- 
lutions per  minute,  it  made  the  dotted  line  diagram  which  figures  219  ;  sup- 
pose we  call  it  219  horse-power,  working  against  the  back  pressure  194.  In 
other  words,  the  boiler  was  yielding  413  horse-power  to  do  219.  Steam  was 
carried  the  whole  length  of  the  stroke  after  it  was  first  admitted.  If  the 
steam  had  been  admitted  at  the  pressure  represented  by  the  line  E,  which  is 
about  sixty  three  pounds,  and  been  cut  off  at  H  E,  expanded  as  shown  by  M 


TWENTY  YEARS  WITH  THE  INDICATOR.  167 

G,  it  would  have  produced  352  horse-power  with  an  expense  of  a  little  less 
than  half  the  steam,  provided  the  valve  had  admitted  the  steain  at  the  outset 
and  the  exhaust  had  not  been  checked.  On  the  other  hand,  had  this  engine 
admitted  the  boiler  pressure  of  one  hundred  pounds,  cutting  it  off  at  F  on  B, 
properly  expanded  and  exhausted,  the  steam  which  was  in  the  boiler  and  was 
not  used  on  account  of  defects  in  the  construction  of  the  engine,  a  still  less 
quantity  of  steam  would  have  given  459  horse-power  as  against  219  horse- 
power by  this  wretched  misuse  of  the  steam. 

The  valves  in  the  engine  from  which  this  diagram  was  taken  are  very 
wrong  in  their  construction,  and  have  a  fault  common  to  many  of  the  new 
engines  of  '83  and  '84.  They  do  not  travel  far  or  fast  enough  to  give  either 
induction  free  from  the  throttling,  or  eduction  free  from  back  pressure ; 
steam  cannot  be  used  profitably  or  economically  without  free  passage — into 
and  out  of  the  engine. 


LESSON  LI. 


HARRIS-CORLISS  ENGINE -DISTORTION  OF  DIAGRAM  BY  THE  INDICATOR 

MOTION. 

The  approximate  value  of  the  correct  reading  of  an  indicator  diagram  is 
something  which  can  be  gained  by  careful  attention  to  facts,  and  we  believe 
only  in  that  way.  Fig.  110  is  a  rather  peculiar  case,  from  a  Corliss  engine 
23  X  48,  running  sixty-six  revolutions,  seventy-nine  pounds  of  steam  at  the 
moment  of  taking,  nearly  eight  pounds  of  back  pressure,  and  was  the  cause  of 
considerable  argument  and  investigation. 

The  line  A  is  absolute  vacuum,  B  atmospheric  line  of  the  instrument,  C 
exhaust  line  of  the  indicator,  D  expansion  line  of  the  instrument,  E  realized 
boiler  pressure  in  the  cylinder,  F  boiler  pressure.  It  will  be  seen  that  the 
engine  takes  steam  very  squarely,  carries  it  for  a  short  distance,  and  immedi- 
ately commences  to  drop  off.  We  have  located  the  base  line,  G,  a  little  beyond 
the  center,  in  order  to  allow  the  steam  time  for  settling  down  to  its  work. 
From  the  intersection  A  G  we  have  drawn  I  E,  and  parallel  to  it  H ;  the 
intersection  of  H  E  by  this  demonstration  gives  us  the  point  at  which  steam 
was  cut  off,  to  give  the  pressure  at  G  in  the  stroke.  The  demonstration  is  made 
for  ascertaining  whether  the  steam  expanded  correctly  or  not  from  the  point 
E  I  j  and  the  line  J,  which  is  dotted  differently  than  the  line  D,  is  the  hyper- 
bolic curve  from  E  I,  or  the  amount  of  steam  used.  Curiously  enough  this  line 


i68 


TWENTY  YEARS  WITH  THE  INDICATOR. 


J  crosses  the  expansion  line  D  at  the  point  G,  or  very  near  it,  and  it  falls 
nearly  as  much  below  the  expansion  line  of  the  instrument  on  finishing  the 
stroke,  as  it  rises  above  it  between  H  I  and  G  H. 


FIG.  110. 

There  is  something  rather  curious  about  the  peculiar  formation  of  this  line, 
as  also  in  the  cutting  off,  and  after  the  question  was  submitted  we  wrote  the 
engineer  that  his  engine  was  either  leaking  or  that  his  attachment  was  wrong, 
which  gave  motion  to  the  indicator — -a,  careful  draft  of  all  the  connections 
settled  the  point  that  the  motion  was  not  square  with  the  engine,  and  that 
the  motion  of  the  paper  barrel  of  the  indicator  was  so  arranged  that  it  ran 
too  fast  and  too  slow  from  distortion  of  the  motion,  and  showed  a  "leaky 
valve "  if  the  motion  had  been  correct — but  the  trouble  was  remedied  by 
throwing  away  a  bad  motion,  and  using  the  pantograph  properly  attached, 
and  the  distortion  ceased. 


LESSON  LH. 


A  CURIOSITY—IN  DIAGRAMS. 

In  Fig.  Ill  we  have  a  rather  knotty  subject,  more  for  the  sake  of  the  infor- 
mation it  contains,  but  also  to  show  the  difference  in  indicator's  performance. 
The  diagram  illustrated  was  taken  from  a  Porter- Allen  engine,  one  of  a  pair, 
right-hand  engine,  back  end,  boiler  pressure  eighty-two,  fifty  scale,  revolu- 
tions 355  per  minute,  Tabor  indicator. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


169 


The  admission  line  A  gets  on  very  well  until  the  piston  of  the  engine 
commences  to  move,  when  an  oscillation  takes  place,  making  a  very  attenua- 
ted-looking figure  8.  Curiously  enough,  the  first  loop  seems  to  be  against 
the  motion  of  the  piston  and  the  next  one  with  it,  as  the  steam  is  introduced, 
and  the  movement  of  the  piston  so  sudden,  carries  the  second  slant  of  the 
pencil  lever  up  above  boiler  pressure  some  twenty  pounds ;  coming  down 
again  as  the  motion  of  the  piston  increases,  crossing  under  B,  making  a  most 
peculiar  curve,  dropping  into  the  saw-tooth,  and  then  upward  by  a  reversed 
curve  or  a  concave,  instead  of  convex  movement,  turning  over  again,  coming 
down  in  the  direction  of  D  ;  and,  if  you  turn  this  wrong  side  up,  you  have  a 
handsome  Roman  nose,  rather  sharp  at  the  point,  or  a  good-looking  saw- 
tooth for  a  hand  saw.  The  peculiarity  of  this,  again,  is  a  convex  instead  of  a 


FIG.  ill. 

concave  movement,  dropping  away  considerably  from  the  theoretical  expan- 
sion line,  which  is  dotted  in.  The  vibrations,  then,  which  take  place  in  the 
expansion  line,  become  less  and  less,  but  continue  until  the  very  end  of  ex- 
pansion and  commencement  of  release.  The  engine  is  working  with  a  con- 
denser, and  the  line  F  is  that  of  the  vacuum.  We  have  erected,  as  nearly  as 
possible,  the  theoretic  point  of  cut-off  from  our  own  system  of  demonstration, 
charging  a  moderate  amount  of  clearance  ;  whether  correct  or  not,  we  do  not 
know.  It  will  be  seen  that  the  demonstration  gives  us  a  close  approximation 
to  what  would  ordinarily  be  termed  the  visible  point  of  cut-off,  or  where  the 
expansion  line  really  commences.  The  second  notch  comes  closely  up  to  the 
theoretical,  the  third  the  same,  while  the  fourth,  fifth  and  sixth  are  slightly 
above.  Whether  this  is  caused  by  any  possible  leak  (which  must  be  very 
trifling),  or  whether  larger  clearance  would  have  made  it  still  below,  we  can- 
not say,  for  in  this  case  we  have  assumed  the  clearance,  and,  to  our  mind,  it 
only  shows  that  there  is  a  certain  analogy  in  the  demonstration,  and  the  actual 
effect  wherever  an  approximation  is  made,  and  it  also  shows  that  the  indicator, 
at  high  speed,  may  possibly  become,  in  a  measure,  entirely  unreliable  in  its 


i7o  TWENTY  YEARS  WITH  THE  INDICATOR. 

readings  of  the  position  of  the  valves — for  in  a  case  of  this  kind  there  is  not 
the  remotest  approximation  to  any  position  from  which  we  could  work  to  ad- 
just the  valves.  The  impact  of  the  steam  entering  the  cylinder  at  the  press- 
ure and  speed  given,  is  something  fearful — and  the  indicator  may  not  have 
had  a  steady  motion,  and  any  irregularity,  or  instability,  in  the  reducing  mo- 
tion would  have  given  the  distorted  lines  shown.  The  engine  from  which 
this  was  taken  does  not  make  any  such  diagram,  and  this  is  introduced  as 
one  of  the  curiosities  of  practice. 

The  question  at  issue  really  is :  What  made  these  funny-looking  crooks 
and  curves  in  this  diagram  ?  It  certainly  was  not  the  engine.  Was  it  the 
motion,  or  was  it  some  defect  in  the  instrument,  or  something  between  the 
instrument  and  the  cylinder  ?  Who  can  tell  ?  This  will  be  something  for 
the  engineers  to  work  over,  and  it  will  well  repay  them  for  any  trouble  they 
may  take.  There  are  some  curious  features  about  it.  This  diagram  was 
taken  nearly  two  years  ago,  but  it  is  just  as  well  worth  studying  now  as  ever 
before,  and,  without  further  information,  we  cannot  attribute  all  the  fault  to 
the  indicator,  or  to  the  engine — but  an  insufficient  spring  in  the  indicator,  or 
a  tampering  with  the  barrel-spring  or  a  pendulum  too  weak  for  the  speed 
and  tension,  either  one  will  accomplish  practically  the  same  result — to  a 
certain  extent,  but  not  to  so  radical  a  change. 


LESSON  LIII. 


ADJUSTING  CORLISS  ENGINE  VALVES. 

This  time  we  have  an  interesting  illustration,  and  we  hope  our  readers 
will  not  get  confused  with  the  several  lines  upon  it.  The  diagram  (Fig.  112) 
in  this  case  represents  an  engine  built  by  one  of  the  best  makers,  and  which 
had  been  abused  most  effectually.  A  shows  the  diagram  in  fine,  dotted  lines, 
after  the  adjustment  was  complete  ,-  B,  a  solid  line,  shows  the  second  stage, 
or  during  valve  adjustment ;  and  C,  a  wavy  line,  shows  where  we  found  it. 
This  is  one  of  a  series  of  diagrams  taken  to  find  out  what  power  parties  were 
using,  with  a  view  to  ordering  a  larger  engine.  Commencing  with  the  dia- 
gram C,  and  ninety-five  pounds  of  steam,  we  obtain  sixty-five  pounds  real- 
ized on  the  piston  in  the  cylinder — a  very  bad  beginning  for  a  Corliss  engine, 
but  the  engine  was  not  to  blame.  Notice  the  two  lines  forming  an  angle  at 
D ;  this  is  about  where  the  line  of  admission  would  have  come  out  if  it  had 
gone  on  at  the  same  ratio,  with  the  pressure  at  that  point ;  but  if  the  press- 


TWENTY  YEARS  WITH  THE  INDICATOR.  171 

ure  had  reached  that  point,  it  would  have  gone  forward  of  D  decidedly, 
owing  to  the  quickening  motion  of  the  piston.  Now,  let  us  see.  The  steam 
valve  does  not  open  ;  the  steam  line  looks  like  an 
old-fashioned  poppet  valve  engine,  which  began 
to  cut  off  the  moment  it  was  open.  It  is  hard 
work  telling  where  expansion  begins  or  ends. 

Having  looked  this  matter  over,  and  finding 
both  ends  were  alike,  we  moved  the  eccentric  a 
little  more  than  half  an  inch  ahead  on  the  shaft, 
so  as  to  quicken  the  time  of  movement.  B  was 
the  result ;  the  valve  opens  considerably  quicker, 
and  it  will  be  noticed  with  this  change  we  have 
eighty-eight  pounds  of  steam.  But  by  this  time 
our  crank  valve  is  working  nicely,  but  the  head 


FIG.  112. 

valve  is  pushed  back  by  the  jimcrank  shaft,  or,  in  other  words,  the 
claw  pushes  the  valve  back  on  its  seat,  so  as  to  get  a  good  hold  and  start 
again  ;  but  this  wont  do,  so  we  must  move  the  eccentric  forward  again, 
which  is  done,  and  we  secure  A,  which  is  just  about  as  well  as  we  can  do. 
We  have  now  ninety-five  pounds  out  of  ninety-seven  ;  take  steam  about  at  the 
right  spot.  Our  crank  valve  at  this  time  is  a  little  too  fast,  so  we  must 
change  that  on  the  jimcrank  by  slowing. 

We  have  not  space  here  to  make  all  the  illustrations  that  would  be 
necessary,  especially  as  regards  the  release  and  compression.  It  will  be  seen, 
however,  in  the  fine  dotted  line,  that  the  compression  and  the  opening  valve 
merge  into  one  line  beautifully.  The  expansion  line  looks  very  nicely,  but 
for  the  sake  of  avoiding  any  confusion  we  have  omitted  any  demonstration, 
the  object  of  this  being  to  impress  upon  our  readers  the  fact  that  the  proper 
way  to  open  the  valve  gives  the  best  possible  use  of  steam  ;  and  the  reader 
who  may  be  informing  himself  with  the  use  of  the  indicator  can  see  here  a 
most  notable  case,  where  the  exact  opening  of  the  valve  gave  a  prompt  cut- 
off, a  beautiful  expansion  line  to  all  appearances,  exhausted  slightly  under  the 
atmospheric  line  and  compressed  so  as  to  make  as  fine  a  line  as  we  need  to 
work  for.  It  is  a  simple  lesson,  but  there  is  a  good  deal  in  it. 

The  whole  thing  was  done  in  less  than  half  an  hour,  and  the  engineer 
and  the  parties  who  were  looking  on,  when  they  came  to  load  the  machine, 
never  saw  it  do  so  well  before.  If  an  engine  runs  right  with  a  light  load,  it 
will  run  well  all  the  way  through,  and  we  have  no  doubt  that  this  engine 
would  have  cleared  itself  creditably  if  it  had  been  running  and  carrying 
steam  as  far  as  it  could  have  done;  but  under  these  circumstances  there 
would  have  been  a  good  deal  of  loss,  for  the  steam  pipes  were  insufficient  to 
earry  any  great  part  of  the  length  of  the  stroke. 


i; 2  TWENTY  YEARS  WITH  THE  INDICATOR. 


LESSON   LIY. 


EXPENSIVE  "  CUT-OFF"  BY  CHEAP  ATTACHMENTS. 

The  diagram,  Fig.  113,  was  sent  us  by  an  engineer  with  the  request  that 
we  lay  out  for  him  the  expansion  curve  from  the  apparent  point  of  cut-off, 
and  as  nearly  as  possible  from  the  cut-off  made  by  the  quantity  of  steam  really 
in  the  cylinder,  according  to  our  method  previously  illustrated,  the  data  of 
the  size  of  the  engine  was  not  given  and  is  immaterial  for  the  purpose  for 
which  he  asks  information.  The  data  which  accompanies  it  is  twenty-four 
spring,  fifty-five  pounds  of  steam  in  the  boiler,  head  end  of  engine,  seventy 
revolutions. 

The  diagram  is  a  peculiar  one,  in  fact  a  most  wasteful  one,  and  for  that 
reason  alone  it  is  given  space. 


FIG.  113. 

The  line  A  is  the  basis  of  our  computation  of  quantity  of  steam  accounted 
for  in  the  center  of  the  expansion  line.  [The  engine  is  supposed  to  be  work- 
ing with  a  cut-off],  B  C  parallel  lines,  B  extending  from  the  intersection  of 
the  vertical  line  and  the  line  of  initial  pressure  D  E,  E  is  the  point  of  cut-off 
established  according  to  this  method  of  ordinate  A,  parallels  B  C,  all  of  which 
are  explained,  in  Lesson  XLH,  as  the  method  of  locating  the  exact  point  of 
cut-off,  taking  the  expansion  of  steam  somewhere  nearest  the  center  or  the 
point  of  least  variation.  F  is  the  atmospheric  line  of  the  instrument.  G  the 
line  of  absolute  vacuum. 

In  answer  to  our  inquirers  we  have  taken  the  visible  point  of  cut-off,  D, 
slightly  beyond  the  sharp  corner,  and,  from  the  intersection  of  the  line  of 
absolute  vacuum  and  the  vertical  line  or  admission  line  proper,  have  laid  out 


TWENTY  YEARS  WITH  THE  INDICATOR.  173 

the  theoretical  curve  according  to  the  method  referred  to  above.  This  line 
terminates  at  H  and  shows  a  decided  change  between  the  visible  point  of 
cut-off  and  the  actual  terminal  lines,  the  point  K  in  the  actual  diagram  being 
twenty-seven  pounds  above  the  vacuum  line  and  the  point  H  being  four 
pounds  above  vacuum  line,  and  the  point  H  is  where  the  terminal  pressure 
should  be  if  T>  is  the  point  of  cut-off  as  it  appears,  and  if  the  valves  close 
tightly. 

Taking  the  line  A  as  the  basis  of  our  calculations,  we  find  the  point  E  to 
be  designated  as  the  cut-off  by  demonstration,  a  termination  of  the 
expansion  line  proper  at  I,  being  1^  pounds  above  the  atmospheric  line  of 
the  instrument,  16^  pounds  above  absolute  vacuum,  while  the  real  line  of  the 
instrument  is,  as  before,  iwenty-seven  pounds  above  absolute  vacuum.  There 
are  some  other  peculiar  features  to  this  diagram ;  in  the  boiler  we  have  fifty- 
five  pounds  steam  pressure,  only  thirty-two  of  which  at  the  outset  is  realized 
in  the  cylinder.  If  we  follow  the  line  of  the  instrument  we  find  that  after 
the  valve  commences  to  close,  somewhere  near  D,  there  is  a  gradual  sifting  in 
of  steam  until  it  passes  the  intersection  of  the  line  A  with  the  expansion  line 
of  the  instrument ;  in  other  words,  the  engine  takes  steam  a  long  way  after 
the  cut-off  valve  appears  to  be  closed,  and  if  there  is  any  economy  in  the 
engine,  it  must  be  economy  in  running  a  cheap  engine  at  an  enormous  expense 
for  fuel.  If  the  reader  will  figure  the  water  consumption  of  this  engine,  for 
comparison  with  any  size  and  speed  engine  he  chooses,  he  will  find  it  is 
enormous. 

The  exhaust  of  the  engine  is  anything  but  good  ;  starting  with  nine 
pounds  of  back  pressure,  averaging  five,  but  perhaps  this  is  not  all  in  the 
engine,  our  informant  does  not  give  us  this  fact.  Whatever  may  be  in  the 
engine  it  is  not  a  good  exhaust.  The  compression  line  is  fair  but  the  steam 
admission  seems  to  be  late,  peculiarly  so  on  the  upper  part  of  the  line  ;  the 
steam-carrying  line,  or  the  steam  line  proper,  is  very  short,  and  while  the 
visible  point  of  cut-off  is  sharp  to  a  certain  extent,  the  practiced  eye  soon 
discerns  that  there  is  no  expansion  line  to  the  diagram.  It  shows  what  is 
termed  sifting  in  of  steam,  until  considerably  past  the  half  stroke. 

In  outline  the  diagram  has  every  appearance  to  us  of  a  peculiar  arrange- 
ment known  as  a  regulating  cut-off,  where  some  sort  of  a  cam  is  applied  to  the 
throttle-valve  regulator,  which  lifts  the  throttle  valve  at  the  commencement 
of  every  stroke  and  drops  it  again.  That  probably  accounts  in  the  action  of 
the  regulator  for  the  peculiar  line  from  between  the  commencement  of  the 
admission  line  and  the  steam  line.  It  is  a  sort  of  combination  which  is  both 
unsatisfactory  and  expensive.  The  visible  point  of  cut-off,  as  our  writer 
terms  it,  at  D,  equals  almost  exactly  one-ninth  of  the  stroke;  while  the 
point  of  cut-off,  supposing  the  valves  were  tight,  or  according  to  the  quantity 
of  steam  used  in  the  center  of  the  expansion  line,  is  shown  at  E,  is  16-45  of 
the  stroke  or  plus  one-third ;  in  other  words  the  engine  is  actually  using  more 
than  three  times  as  much  steam  as  is  shown  by  the  indicator  diagram  at  a 
casual  glance  and  without  the  application  of  some  test  to  determine  it.  This 
is  readily  shown  by  the  very  great  height  of  the  termination  of  the  expansion 


174  TWENTY  YEARS  WITH  THE  INDICATOR. 

line  above  absolute  vacuum.  The  cutting  off  of  thirty-two  pounds  of  steam, 
where  we  should  have  fifty-five  pounds,  with  a  terminal  pressure  of  twelve 
pounds  above  the  atmospheric  line,  is  eleven  pounds  too  much  at  the  termi- 
nation of  the  expansion,  and  is  just  about  in  that  ratio  to  the  economical  use 
of  steam,  as  is  shown  in  this  case. 


LESSON  LY. 


THE  CORLI8S  OR  MODERN  COMPOUND  HIGH  DUTY  PUMPING  ENGINE. 

Figs.  114  and  115  are  from  the  Corliss  Pumping  Engine  at  Pawtucket, 
R.  I.  It  has  been  running  several  years  in  charge  of  one  of  the  most  intelli- 
gent and  painstaking  of  engineers,  Mr.  John  H.  Walker. 

Fig.  114  is  from  the  high-pressure  cylinder,  15  inches  in  diameter,  30 
inches  stroke,  making  47  revolutions  per  minute,  scale  60,  steam  pressure  132 
pounds,  Corliss  upright  boilers  being  used,  130  pounds  are  realized  on  the 
piston  and  the  steam  line  is  carried  as  straight  as  is  possible  to  the  point  of 
cut-off.  The  expansion  line  is  a  marvel  of  beauty  and  correctness ;  the  release 
is  early  and  the  exhaust  into  the  receiver  shows  a  commencement  of  ten 
pounds  receiver  pressure  and  a  terminal  of  eight  pounds,  there  is  very  little 
rise  in  the  pressure  in  this  case.  The  admission  could  hardly  be  better.  The 
demonstration  in  this  case  precludes  the  possibility  of  drawing  the  theoretical 
line  a  portion  of  the  way,  as  the  lines  would  pass  one  over  the  other.  Very 
little  compression  is  used ;  that,  for  some  reason  unknown  to  us,  is  one  of  Mr. 
Corliss'  ideas,  to  work  with  little  or  no  compression.  There  is  a  very  slight 
difference  between  the  apparent  cut-off  and  the  theoretical,  but  it  is  so  ex- 
ceedingly slight  as  to  be  almost  unworthy  of  notice  from  a  critical  stand- 
point. 

115  is  from  the  low-pressure  cylinder  of  the  same  engine,  the  cylinder 
being  30  inches  in  diameter,  30  inches  stroke,  running  47  revolutions  per 
minute,  scale  12.  114  is  from  the  front  end  of  the  high-pressure  cylinder, 
and  115  from  the  back  end  of  the  low-pressure  cylinder.  From  the  ten  pounds 
in  the  receiver,  we  have  nine  pounds  initial  pressure,  gradually  falling  off  to 
seven  pounds  before  the  close  of  the  valve,  expanding  to  seven  and  one-half 
pounds  below  the  atmospheric  line.  The  condenser  takes  hold  at  twelve  and 
one-half  pounds,  the  maximum  vacuum  being  about  thirteen  and  one-half 
pounds,  or  very  nearly  approximating  to  the  theoretical.  The  demonstrat 


TWENTY  YEARS  WITH  THE  INDICATOR.  175 

in  this  case  shows  a  very  close  approximation  of  the  actual  to  the  theoretical, 
taking  into  account  the  lowest  pressure  from  the  initial  and  the  point  of 
cut-off. 

This  engine  has  been  running  some  eight  years,  and  these  diagrams  were 
selected  from  the  regular  indication  of  each  day.  .  Comparing  the  two  dia- 
grams one  with  the  other,  the  high-pressure  gives  about  the  highest  possible 
effect  of  steam,  and  the  low-pressure  gives  almost  the  maximum  efficiency 
of  the  receiver  pressure  for  the  distance  which  it  is  carried.  We  have,  there- 
fore, a  very  fine  result  economically,  and  through  the  courtesy  of  the  engineer 
we  are  furnished  with  the  following  facts  from  his  regular  log-book,  which 
has  been  carefully  kept  every  day  since  the  engine  was  delivered  to  the  Water 
Board.  This  engine  was  originally  built  to  supply  the  town  of  Pawtucket ; 
since  that  time  they  have  added  a  very  large  mileage  of  pipe  and  a  large 
amount  of  water  to  the  supply,  so  that  the  pumping  engine  is  now  furnishing 
double  what  it  was  originally  intended  to  do,  and  this  over  a  very  scattered 
area  of  territory.  The  engine  is  now  running,  November,  1884,  twenty-four 
hours  per  day,  the  actual  amount  of  coal  consumed  is  216  pounds  per  hour ; 
Wilkesbarre  egg  coal  is  used,  which  costs  $4.35  per  ton  of  2,000  pounds, 
screened  ;  the  amount  of  ashes  is  nearly  twelve  per  cent,  and  when  we  say 
216  pounds  of  coal  per  hour,  this  is  the  actual  amount  of  coal  fed  into  the 
furnace,  no  allowance  being  made  for  anything.  The  pumps  of  this  engine 
are  now  working  under  a  head  of  272  feet.  The  high-pressure  diagram 
figures  72.658  horse-power,  the  condensing  cylinder  figures  65.398  horse- 
power, making  138.056  ;  the  variation  between  the  two  ends  is  very  trifling. 
Taking  the  coal  which  is  actually  consumed  we  have  1.57  pounds  per  horse- 
power per  hour  ;  taking  the  combustible  we  have  1.39+  pounds  per  hour,  per 
horse-power.  Taking  the  cost  of  the  power  in  dollars  and  cents,  calling  all 
coal,  we  have  3.4  mills  per  horse-power  per  hour,  while  if  we  figure  the  com- 
bustible, we  have  the  cost  of  one  horse-power,  per  hour  as  3.02  mills. 

The  duty  under  the  Board  of  Experts'  test,  was  133,522,060  foot-pounds 
for  one  hundred  pounds  of  coal.  Mr.  Corliss  took  exception  to  this,  and  de- 
nominated it  the  "  humbug  "  test  from  the  fact  that  allowances  were  made. 
An  absolute  test  made  afterwards  by  the  same  Board  on  Mr.  Corliss'  basis 
gave  it  a  duty  of  104,357,654  foot-pounds  per  hundred  pounds  of  coal,  and 
this  duty  has  been  somewhat  exceeded  in  its  regular  every-day  work,  while 
in  charge  of  its  efficient  chief.  The  duty' from  the  time  of  its  start,  January 
31st,  1878,  to  the  6th  of  November,  1878,  was  on  fuel  consumed  to  pump, 
106,234,300  foot-pounds.  In  June  1882,  the  engine  was  stopped  for  inspec- 
tion and  the  piston  rod  in  the  low-pressure  cylinder,  where  it  passes  through 
the  plunger  in  the  pump,  was  found  to  be  so  corroded  by  the  action  of  water, 
that  it  was  necessary  to  have  a  new  piston-rod.  This  was  the  first  repair 
made  upon  the  engine.  The  duty  of  the  engine  for  the  twelve  months  ending 
January  1st,  1883,  was  113,439,331  pounds  of  water  raised  one  foot  high  with 
a  hundred  pounds  of  coal,  counting  all  coal  used  with  no  deduction  for  ash 
or  cinders. 


iy6  TWENTY  YEARS  WITH  THE  INDICATOR. 

It  has  been  a  most  gratifying  success,  both  in  economy,  durability,  lack 
of  repair  bills ;  and  the  diagrams  show  if  not  the  highest,  certainly  a  very  high, 
economy  considered  from  any  point,  taking  advantage  of  no  technicalities, 
allowances  or  possibilities.  These  diagrams  may  be  studied  critically,  in 
comparison  with  those  in  some  of  the  preceding  lessons,  where  compound 
engines  of  foreign  builders  are  compared,  and  with  favor  to  Mr.  Corliss,  upon 
grounds  of  absolute  fact,  with  no  assumed  allowances  of  any  kind. 


FIG.  114. 


"*•*«•-. 


FIG.  115. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


177 


LESSON  LVI. 


SHORT  CONNECTIONS  TO  THE  ENGINE,  WITH  NO  CHANGE  OF  POSITION 
FROM  THE  THREE-WAY  COCK  ATTACHMENT  IN  FIG.  117. 

Diagram  Fig.  116  is  one  which  is  somewhat  peculiar  in  respect  to  an  ex- 
cessive cushion.  It  is  taken  from  one  of  the  new  Buckeye  engines,  running 
222  revolutions  per  minute,  with  a  steam  pressure  at  the  moment  of  92 
pounds,  scale  50,  Thompson  improved  indicator. 

In  justice  to  the  engine  we  will  say,  the  party  in  charge  was  partial  to  the 
three-way  cock  for  indicating,  and  Fig.  116  was  taken  from  the  same  engine, 
with  not  the  least  change  of  valves  from  Fig.  117.  Let  the  reader  compare 
the  two  outlines. 

In  this  case,  A  equals  the  vacuum  line,  B  the  atmospheric  line,  C  boiler 
pressure  at  the  moment  of  taking,  D  highest  pressure  by  compression,  E 
point  at  which  the  exhaust  valve  closed  on  the  return  stroke.  In  this  case, 
the  exhaust  valve  closed  at  about  3|-  inches  before  the  end  of  the  travel,  and 


FIG.  116. 

although  the  engine  was  exhausting  very  freely,  in  fact,  without  any  per- 
ceptible back  pressure  on  the  indicator,  it  will  be  seen  that  at  the  point  F,  a 
little  more  than  a  quarter  inch  from  the  end  of  the  stroke,  the  compression 
amounted  to  113  pounds.  From  F,  the  rest  of  the  stroke,  there  appears  to 
have  been  a  slight  leak,  a  portion  of  which  was  undoubtedly  in  the  indicator, 
and  some  of  it  may  have  been  in  the  piston  or  valves  of  the  engine,  so  that 
from  the  point  F  the  pressure  falls  away  to  the  angle  indicated  by  the  dotted 


178  TWENTY  YEARS  WITH  THE  INDICATOR. 

line  G.  From  this  angle  it  will  be  noticed  that  the  pressure  continues  to  fall, 
while  the  engine  had  passed  the  center  and  the  indicator  had  commenced  to 
move  again  in  the  direction  of  the  outward  stroke  ;  G  indicates  the  point  at 
which  the  crank  passed  the  exact  center  of  the  return  stroke,  and  commenced 
its  outward  stroke ;  meanwhile  the  steam  pressure  slightly  drops  until  H  is 
reached,  which  give  us  between  87  and  88  pounds  initial ;  from  H  to  I  the  steam 
is  carried,  and  at  I  the  steam  valve  commences  to  close. 

The  peculiar  angle  formed  by  the  line  dropping  from  its  highest  point,  F, 
is  caused  by  a  fall  of  pressure  while  the  engine  completes  the  last  portion  of 
the  stroke,  the  angle  in  the  line  F,  H,  shows  the  precise  point  where  the  mo- 
tion of  the  engine  changes,  and  after  the  motion  has  changed  the  pressure 
still  continues  to  fall,  showing  that  the  valves  of  the  engine  were  in  a  splen- 
did condition  and  were  tight.  At  H  we  have  the  first  real  evidence  of  the 
steam  valves  opening,  and  the  steam  line  crosses  the  compression  line,  making 
the  steam  line  H  I.  Here  we  have  another  most  interesting  example  of  the 
efficiency  of  the  indicator  when  correctly  applied,  and  its  lines  correctly  read 
from  the  diagram.  In  many  cases  such  a  compression  line  would  be  at  once 
called  an  early  admission  line  or  "  taking  steam  too  quick  " — but  such  is  not 
the  case.  v. 

Now,  to  analyze  the  diagram  for  efficiency,  we  will  commence  our  demon- 
strations by  the  line  K,  the  actual  pressure  at  K  gives  us  an  absolute  cutting  off 
of  the  pressure  of  steam  realized  at  C,  J,  so  that  while  the  valve  commences  to 
close  at  I,  apparently  it  becomes  closed  at  J,  or  very  nearly  so ;  from  J  to  K 
the  theoretical  curve  runs  slightly  above  or  outside  of  the  actual  curve  of  the 
instrument ;  from  K  to  L,  the  point  of  commencement  of  release,  the  theo- 
retical line  runs  slightly  under  the  actual  line  of  the  instrument.  The  release 
is  most  excellent,  and  it  commenced  under  about  twelve  pounds  pressure, 
making  a  very  clear  exhaust  and  commencing  to  compress  or  cushion  too 
early  and  making  the  loop.  The  particular  feature  of  this  loop  is  a  very  con- 
siderable shock  to  the  engine ;  in  fact,  there  is  quite  too  much  compression, 
and  if  the  engineer  will  reduce  this  compression  by  one-half,  his  engine  will 
sail  over  the  center  much  easier,  and  without  so  much  wear  and  tear  on  the 
connections,  brasses,  etc,  The  boiler  pressure  in  this  case  is  very  hand- 
somely realized,  showing  that  the  makers  of  the  engine  have  made  considera- 
ble improvement  in  proportion  and  motion  of  their  valves. 

Taken  all  in  all,  the  admission  and  expansion,  release  and  exhaust  lines 
of  the  diagram  are  excellent,  the  compression  is  no  fault  of  the  design  or 
mechanical  part  of  the  engine,  if  the  compression  is  reduced  to  less  than  one- 
half  the  amount  shown  here.  The  engine  will  do  more  work  with  the  same 
steam,  and  will  regulate  better  without  any  doubt.  It  is  not  policy  to  com- 
press twenty  pounds  above  the  initial  pressure  you  are  working  with  ;  it  does 
not  make  the  valves  last  any  longer,  or  work  any  easier ;  it  causes  entirely 
too  much  strain  on  the  brasses  and  connections,  and  is  bad  policy  every  way. 
The  dotted  line  M,  from  the  line  J  to  the  vertical  line  at  the  end  of  the  dia- 
gram, gives  the  volume  of  the  cylinder  filled  with  steam,  simply  for  the  pur- 
pose of  computation. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


179 


This  lesson  is  a  most  complete  demonstration  of  the  lack  of  reliability  of 
the  three-way  cock  attachment,  when  used  to  adjust  the  valves.  Fig.  116 
was  taken,  close  connection,  on  each  end  of  the  cylinder,  only  one  end  shown. 


LESSON  LVII. 


THREE-WAY  CONNECTIONS  FROM  SAME  ENGINE  AS  LESSON  LVI. 

The  old  way  of  side  pipe  and  three-way  cock  still  exists.  It  is  entirely 
useless  for  adjustment  of  valves  or  for  any  other  than  approximation  to 
power,  position  of  valves,  or  realized  pressure. 

The  reader  will  find  food  for  thought  in  carefully  comparing  diagrams, 
Figs.  116  and  117,  with  each  other — both  were  taken  from  the  same  engine, 
with  no  sort  of  change  except  the  side  pipe  and  three-way  cock  were  used  in 
Fig.  117  and  taken  off  in  116,  the  spring  of  indicator  being  changed  to  suit 
the  increased  boiler  pressure  in  116. 


">.. 

X        ,*' 

\/ 

/5S. 

V 


FIG.  117. 

Figure  117  was  taken  from  a  Buckeye  engine,  made  by  the  Buckeye 
Engine  Company  of  Salem,  Ohio,  nine  inches  diameter  of  cylinder,  fourteen 
inches  stroke,  225  revolutions  by  the  counter,  eighty-five  pounds  of  steam  in 
the  boiler,  throttle  valve  wide  open,  scale  of  spring,  forty,  Thompson  im- 
proved indicator.  This  engine  was  on  exhibition  at  the  American  Institute 
Fair,  New  York,  and  is  one  of  the  Buckeye  Improved.  The  makers  have  for 


i8o  TWENTY  YEARS  WITH  THE  INDICA  TOR. 

the  past  year  been  making  changes,  with  a  view  of  improving  the  economy, 
the  regulation  and  the  action  of  their  engine. 

The  engine  was  running  electric  lights,  and  this  will  plainly  tell  of  any 
trouble  in  regulation.  The  diagram  117  was  taken  upon  one  of  our  own  in- 
dicators, but  it  has  just  this  defect,  it  was  taken  by  a  three-way  cock  in  the 
center  of  the  cylinder,  a  thing  which  we  disapprove  of,  from  the  fact  that  it 
introduces  inaccuracies.  The  steam  had  entirely  too  much  water  in  it,  but 
that  should  not  be  taken  into  account  against  the  engine. 

The  application  of  the  theoretical  curve  to  the  diagram  shows  a  very  good 
action  indeed  of  the  valve,  and  we  have  taken  the  highest  pressure  realized 
at  the  moment  of  impact,  and  it  will  be  noticed  that  the  theoretical  curve 
follows  down  past  the  center  of  the  stroke,  almost  on  the  actual  line  of  the 
instrument.  Below  the  center  or  half-stroke,  as  the  motion  is  changed  from 
fast  to  slow,  the  actual  line  of  the  instrument  rises  somewhat  above  the  theo- 
retical. This  may  be  caused  by  the  change  in  the  pressure  and  the  amount 
of  water  present ;  it  probably  is  not  any  fault  of  the  valves.  The  action  of 
the  valves  on  this  engine  is  certainly  very  good.  It  is  one  of  the  best 
Buckeye  engine  diagrams  we  ever  saw,  and  if  the  improvements  are  up  to  this 
quality  of  work,  the  engine  will  do  better  work  than  ever  before,  and  give  the 
best  results. 

We  have  only  made  the  theoretical  curve  upon  one  of  the  cards.  There 
are  several  points  in  it  to  study,  particularly  the  action  of  the  steam  valve  in 
taking  steam,  the  difference  in  compression  as  between  the  two  ends.  This 
short  diagram  was  made  use  of  because  we  refused  to  take  a  diagram  from 
another  instrument  of  greater  length,  which  does  not  show  the  oscillations  in 
the  expansion  line,  and  makes  quite  a  difference  as  between  the  compression 
shown  by  the  Thompson.  We  would  call  especial  attention  to  the  serrations 
or  fluctuations  in  the  expansion  line,  which  show  the  most  delicate  action  of 
the  indicator — and  the  variations  caused  by  rapid  expansion  and  changes  of 
temperature,  pressure,  etc. 

These  diagrams  bear  close  examination,  and  are  a  very  close  approxima- 
tion to  the  theoretical  expansion,  bearing  in  mind  that  tha  position  of  the 
valves  and  their  action  as  to  motion  are  erroneously  shown  by  that  attachment, 
which  should  be  prohibited  everywhere — e,  three-way  cock  am!  long  side  pipe. 
[See  lesson  LVI  in  connection  with  LVIL] 


TWENTY  YEARS  WITH  THE  INDICATOR. 


181 


LESSON  LYIII. 


HIGH  COST— LOW  ECONOMY  STEAM  YACHT  COMPOUNDS. 

Fig.  118,  H.  P.,  119,  L.  P.,  are  a  pair  of  diagrams  from  one  of  the  rich  men's 
fancy  yachts,  more  expensive  than  fast.  118  is  the  high-pressure  diagram  which 


FIG.  118. 


FIG.  119. 


came  to  us  without  any  atmospheric  line  ;  119  is  the  low-pressure  diagram  ; 
the  scale  of  the  high-pressure  being  fifty  to  the  inch.  We  have  assumed  the 
dotted  line  as  atmospheric  line  in  Fig.  118,  at  slightly  an  excess  of  the  realized 
pressure  on  the  low-pressure  diagram,  which  is  sixteen  per  inch.  We  have 


t82  TWENTY  YEARS  WITH  THE  INDICATOR. 

twenty-six  pounds  realized  pressure  on  the  low-pressure  cylinders  ;  on  the 
high-pressure  cylinders  we  have  made  no  demonstration,  from  the  very  fact 
that  we  are  not  certain  of  our  data,  and  at  the  best  they  are  as  wretched 
diagrams  as  were  ever  taken  from  anything  in  the  shape  of  a  steam  engine. 
Those  who  are  interested  will  understand  that  a  link  motion  is  used,  but  it 
must  be  a  sorry  link  which  makes  such  a  use  of  steam  as  is  shown  in  the  steam 
line  of  the  solid-drawn  diagram.  In  Fig.  118  the  admission  line  commenced 
very  well,  but  when  the  steam  line  begins  it  is  a  curious  line ;  really  there  is 
no  cut-off  to  it,  the  expansion  line  is  a  fearful  one,  and  not  economical  or  cor- 
rect, and  is  convex  instead  of  concave,  and  when  it  comes  down  toward  .he 
release,  the  line  instead  of  being  an  expansion  is  turned  into  saw-teeth.  Like 
most  compound  engines,  the  exhaust  line  is  considerably  higher  in  the  center 
than  at  the  commencement.  This  is  all  natural  enough,  but  when  we  turn  to 
the  dotted  line  on  Fig.  118,  we  have,  if  anything,  a  worse  line  than  the  solid 
line  in  the  diagram ;  a  peculiar  jump  about  the  commencement  of  release  we 
are  unable  to  account  for  satisfactorily  to  ourselves,  but  which  is  probably 
caused  by  low-pressure  cylinder  valves. 

If  the  party  who  took  the  diagrams  had  been  careful  to  draw  in  his  at- 
mospheric line,  we  should  have  been  pleased  to  make  a  demonstration.  We 
have  drawn  in  the  atmospheric  line  at  about  what  we  supposed  it  should  be 
drawn,  and  this  gives  us  full  initial  pressure  105  pounds,  as  the  throttle  valve 
is  wide  open,  and  the  link  full,  scale  fifty.  On  the  low-pressure  card  we  have 
something  more  to  work  by,  for  in  this  case  the  atmospheric  line  is  properly 
drawn  in  by  the  instrument,  scale  sixteen,  link  up  full,  speed  in  both  cases 
126,  wide  open.  Here  we  have  an  impact  initial  pressure  of  twenty-six  pounds, 
a  vacuum  of  about  nine  pounds.  The  cut-off  is  very  well  defined  in  the  solid 
line  and  less  so  in  the  dotted.  We  have  made  two  demonstrations  here,  one 
with  the  dotted  line  and  the  other  with  the  solid  line.  The  dotted  line  is  to 
ascertain  whether  the  steam  expands  under  the  generally  conceded  theoretical 
law  after  expansion  apparently  commences.  The  solid  line  shows  what  ought 
to  have  been  done  at  the  actual  pressure  at  the  point  of  cut-off  which  is  visible. 
We  start  with  a  pressure  of  twenty-three  pounds  ;  at  a  little  past  half  stroke 
it  runs  down  to  13^,  and  the  diagram  line  of  the  indicator  shows  that  the 
valve  closes.  The  dotted  line  shows  that  the  valves  were  practically  tight, 
for  the  pressure  falls  away  triflingly,  if  we  take  the  commencement  of  release, 
or  just  prior  to  that  point,  as  the  basis  of  that  computation.  But  if  we  take 
the  actual  pressure  before  the  valve  becomes  positively  closed  on  the  line,  we 
find  that  the  general  ratio  of  expansion  is  closely  on  the  theoretical,  under- 
standing always  that  there  will  be  more  variation  in  the  link  motion  than  in 
the  positive  eccentric  and  lever  or  rock  or  wiper  motion.  Now,  if  we  use  our 
sixteen  scale  as  a  rule,  we  find  the  solid  line  from  which  our  demonstration  is 
made  to  be  twenty-five  inches  (call  it)  from  the  commencement  of  the  stroke. 
At  this  point  13£  pounds  of  steam  were  cut  off,  having  been  reduced  in  press- 
ure from  twenty-three,  and  carried,  we  will  say,  twenty -five  inches.  Now  if 
the  pressure  had  been  realized  it  would  have  required  only  eighteen  inches, 
cut  off  at  twenty-three  pounds,  or,  in  other  words,  it  would  have  required 


TWENTY  YEARS  WITH  THE  1MDICA  TOR.  183 

18-25,  or  two-thirds,  practically,  the  amount  of  steam  it  did  require.  The 
high-pressure  diagram  is  abominable,  and  the  use  of  steam  is  without  any 
sort  of  economy,  the  pressure  drops  rapidly  both  on  high  and  low-pressure 
cylinders  after  the  valve  gets  open.  In  the  low-pressure  cylinder  there  may 
be  some  excuse  from  lack  of  volume,  or  pressure  varying  in  receiver,  but  in 
the  high-pressure  cylinder  it  is  choked  or  wiredrawn  by  insufficient  ports  or 
pipes. 

These  engines  were  built  in  1883.  It  is,  perhaps,  needless  to  say  that 
this  is  not  the  fastest  yacht  in  the  world  by  any  means,  and  whoever  the 
builder  may  be,  he  need  not  consider  himself  particularly  nattered  with  this 
kind  of  result,  if  economy  is  to  be  considered  at  all. 


LESSON   LIX 


ANOTHER  OCEAN  S.  S.  COMPOUND  ENGINE. 

We  hear  so  much  of  the  economy  of  some  of  the  new  ocean  steam- 
ships that  it  will  do  us  much  good,  perhaps,  to  examine  some  of  the 
results  of  the  work  of  the  engines,  and  for  that  reason  diagrams,  Figs.  120  and 
121,  from  the  high  and  low-pressure  cylinders  of  a  compound  engine  are 
introduced ;  the  high-pressure  cylinders  of  which  are  seventy-two  inches  di- 
ameter, sixty-six  inches  stroke,  fifty-four  revolutions,  seventy  pounds  boiler 
pressure,  scale  thirty-two.  The  same  letters  apply  to  the  same  lines  on  each 
for  comparison.  On  the  high-pressure  diagram  steam  is  cut  off  at  about 
18-49  of  the  stroke.  Starting  with  a  boiler  pressure  of  seventy  pounds,  E, 
and  do  not  get  within  seven  pounds  of  it  on  the  piston.  There  is  very  little 
approach  to  an  expansion  line,  and  no  one  can  tell  where  the  valve  closes 
from  the  appearance  of  the  line.  In  fact,  there  is  no  marked  feature  of  it  to 
show  where  any  expansion  takes  place. 

The  steamer  in  question  has  been  built  several  years,  and  is  not  by  any 
means  the  fastest  or  the  most  economical  now  afloat ;  she  was  built  to  ac- 
complish a  certain  purpose  and  has  done  it,  but  she  has  never  been  economical 
with  fuel  to  the  extent  that  some  of  the  more  modern  compound  engines  have 
been  except  by  remote  approach. 

Making  a  the  base  of.  our  computation,  give  us  B,  E,  point  of  cut-off  and 
volume,  reference  letters  the  same  in  both  diagrams.  From  B,  the  pressure 
given  at  a,  the  line  F  shows  us  what  power  should  have  been  exerted  and  where 
the  steam  should,  under  ordinary  conditions,  have  been  cut  off  and  expanded 


TWENTY  YEARS  WITH  THE  INDICATOR. 


to.  It  will  be  seen  that  the  boiler  pressure  is  not  realized,  cut-off  is  entirely 
lacking  in  denniteness,  and  the  end  of  the  expansion  is  considerably  above  that 
point  which  the  actual  pressure  at  a  gives  from  the  cut-off  B,  E,  showing 
clearly  that  there  is  either  a  very  radical  error  in  the  indicator  motion,  which 
is  hardly  probable,  or  if  we  look  at  the  low-pressure  cylinder,  or  that  the 

valve  is  slow  in  closing,  or 
that  the  valve  leaks,  which  is 
the  most  probable  reason  of 
all,  for  we  are  certain  that  the 
valve  closes  slowly — from  the 
course  of  the  line.  The  high- 
pressure  cylinder  exhausts 
under  a  pressure  of  about 
eleven  pounds  to  start,  at  the 
center  it  is  fifteen,  and  at  the 
commencement  of  compres- 
sion it  is  almost  fourteen. 
The  admission  line  is  a  little 
late  in  the  opening  of  the 
valve,  and  the  rounding  over 
at  the  corner  is  not  of  neces- 
sity due  to  the  link  motion 
which  was  used,  but  rather 
to  some  little  give  or  play, 
or  what  is  usually  termed 
lost  motion.  We  cannot  con- 
sider this  as  a  very  econom- 
ical diagram,  there  "is  too 
much  loss  in  realizing  the 
boiler  pressure,  and  a  wire- 
drawing of  the  steam,  (if 
tight  valves)  and  the  exhaust 
of  high-pressure  cylinder  into 
receiver  is  fully  as  high  as  it 
should  be,  and  much  higher 
than  the  low-pressure  util- 
izes. The  expansion  line  is 
not  nearly  as  good  on  the 
high  as  the  low-pressure 
cylinder. 

Taking  the  low-pressure  card  made  at  the  same  time,  E  representing  the 
initial  pressure  from  the  high-pressure  cylinder  or  receiver,  a  the  base  line, 
gives  us  B  as  the  volume  of  cylinder  at  which  the  valve  should  have  closed  to 
have  made  the  pressure  at  a,  and  in  this  case  we  have  a  tighter  valve  and  a 
very  much  better  condition  of  circumstances,  showing  but  exceedingly  trifling 
variation  as  between  the  theoretical  and  actual,  taking  the  pressure  at  a  from 


120. 


TWENTY  YEARS  WITH   THE  INDICATOR. 


185 


which  to  make  our  demonstration.  In  this  case  the  pressure  is  a  variable 
quantity,  changing  from  one  to  the  other  cylinder  in  exhausting  and  the  acceler- 
ation of  speed  of  the  piston,  as  well  as  in  condensation,  which  may  take  place 
in  the  passage  or  in  the  receiver,  so  that  we  lose  somewhat  in  the  low-press- 
ure cylinder  from  what  should  be  the  initial  pressure  if  we  had  received  the 
whole  eleven  pounds  from  the  exhaust  of  the  high-pressure  cylinder,  passing 
through  the  ports  and  into  the  low-pressure  cylinder.  We,  therefore,  get 
only  nine  pounds  realized,  and  lose  again  before  cutting  off  about  four  pounds 
more,  expanding  below  the  atmospheric  line ;  in  this  case  we  have  ten 
pounds  vacuum  in  the  condenser  to  start  with,  and  this  is  held  very  well 
until  more  than  two-thirds  of  the  stroke  has  been  made. 

Here  is  an  answer  to  those  people  "  who  do  not  believe  any  cushion  can 
be  obtained  in  the  low-pressure  cylinder  ;"  if  not,  then  what  makes  the  com- 
pression in  this  diagram  ?  It  commences  to  compress  at  about  7-45  of  the 
stroke,  say  one-sixth.  The  admission  line  is  very  square,  and  the  admission 


!\ 


FIG.  121. 

and  carrying  of  steam  in  the  lower-pressure  cylinder  is  better  than  it  is  into 
the  high-pressure.  The  expansion  line  and  the  theoretical  line  very  nearly 
coincide  through  the  major  part  of  the  distance  from  pressure  at  base  line  a, 
showing  conclusively  that  the  valves  in  this  case  do  not  leak  and  that  the  dif- 
ference in  the  high-pressure  diagram  (probably  taken  by  the  same  motion) 
cannot  be  in  the  motion  but  is  in  the  valve.  A  decided  falling  off  from 
pressure  that  under  the  circumstances  should  hardly  be  allowable,  and  about 
two-thirds  the  vacuum  that  should  be  realized  is  obtained. 

We  do  not  know  the  precise  percentage  of  coal  this  steamer  is  now 
burning,  but  it  was  very  largely  in  excess  of  some  of  the  later  steamers  at  the 
last  time  we  knew  of  it.  The  lower-pressure  cylinder  is  120  inches  in 
diameter,  sixty-six  inches  stroke,  fifty-four  revolutions  per  minute,  scale 
twelve,  pressure  variable.  It  may  interest  some  of  our  readers  to  figure  the 
power  in  these  diagrams  from  the  data  given.  The  low-pressure  cylinder 


1 86 


TWENTY  YEARS  WITH  THE  INDICATOR. 


cuts  off  at  about  17-45  of  the  stroke,  starting  with  an  initial  pressure  of  nine 
pounds,  cutting  off  at  a  pressure  of  a  trifle  over  4J  pounds  ;  the  commence- 
ment of  release  is  four  pounds  under  the  atmospheric  line,  which  shows  a 
very  good  grade  of  expansion.  But  we  must  not  expect  perfection  in  these 
large  engines,  although  we  might  probably  attain  higher  results  of  duty  than 
these  particular  diagrams  show.  The  principles  of  adoption  are  the  same — 
economy,  speed,  etc., — as  with  the  stationary  engines.  There  is  plenty  of  data 
here  to  figure  from,  and  it  would  be  interesting,  for  those  who  care  to  take 
the  trouble,  to  solve  the  points  of  ratio  of  expansion,  the  amount  of  water 
power,  etc. 


LESSON   LX. 


AN  EXPERIMENT  BY   AN  ENGINE   BUILDER. 


FIG.  122. 

Fig.  122  is  from  the  first  engine  of  a  new  builder  for  the  especial  purpose 
of  electric  lighting.  The  data  is:  Boiler  pressure  70,  spring  40,  diameter 
10§,  stroke  12  inches,  revolutions  115. 

To  attempt  to  demonstrate  all  the  faults  in  this  engine  would  be  to  do 
work  which  should  have  been  done  by  its  designer  and  builder ;  for  this  we 
have  neither  the  space  nor  the  disposition.  This  is  evidently  a  very  bad  imi- 
tation of  a  well-known  engine.  Taking  initial  pressure,  seventy  pounds 
boiler  pressure ;  to  economize  room  we  have  traced  the  dotted  line  card,  show- 
ing the  same  engine  under  a  little  different  load.  We  have  fifty-six  pounds 


TWENTY  YEARS  WITH  THE  INDICATOR.  187 

initial  pressure  out  of  seventy.  This  in  itself  will  condemn  the  engine,  pro- 
viding the  connections  are  free.  The  engine  starts  off  with  a  round  instead 
of  a  square  corner  between  the  admission  line  and  the  steam  line.  With  an 
initial  pressure  of  fifty-one  pounds,  gradually  rising  to  almost  fifty-five,  and  at 
about  the  point  where  the  cut-off  appears  to  take  place,  we  find  between  forty- 
five  and  forty-six  pounds  of  pressure,  having  fallen  off  ten  pounds  in  carry- 
ing steam  four-tenths  of  the  stroke.  The  engine  commences  to  release  with 
a  pressure  of  seventeen  pounds  on  the  piston,  releases  very  well,  but  does  not 
get  down  in  the  exhaust  to  the  atmospheric  line ;  compression  starts  at  rather 
more  than  half  the  distance  that  the  steam  is  carried.  The  compression  line 
here  may  have  been  shaken  up  by  a  poor  foundation,  but  more  probably  by  a 
constant  changing  of  pressure  in  the  compression  in  the  solid  line  card,  but 
in  the  dotted  line  the  compression  line  is  a  very  queer  one,  and  the  little 
hook  at  the  extreme  end,  with  the  peculiar  formation  of  the  steam  line,  in 
starting  on  to  take  steam  for  the  stroke,  shows  that  the  valve  does  not  open 
as  wide  with  a  light  load  as  with  a  heavy  one.  Notice  that  the  steam  is  cut 
off  at  a  very  much  lower  pressure  in  the  light  load,  proportionately,  than  the 
full  load,  on  the  larger  diagram  of  the  two.  Whatever  makes  the  funny  jog 
in  the  dotted  line  on  the  expansion  line  after  cut-off,  or  whether  the  steam  is 
carried  to  that  point  of  the  indentation  and  then  the  cut-off  actually  takes 
place,  we  are  a  little  at  a  loss  to  tell  from  the  appearance,  and  the  card  has  no 
value  in  an  economical  way. 

The  diagram  is  very  uneven,  and  contains  so  many  faults  that  we  have 
not  cared  to  give  the  time  to  a  demonstration  on  the  expansion  curve.  This 
engine  would  be  most  decidedly  lacking  in  economy ;  whatever  its  regulation 
may  be  we  do  not  know,  but  it  was  evidently  built  by  some  man  who  has  not 
progressed  into  the  new  style  of  valve  motion,  for  the  valves  do  not  travel 
correctly  nor  far  enough.  Whatever  their  proportions  of  ports  may  be  we  do 
not  know ;  one  thing  is  sure,  it  is  too  small,  either  by  insufficient  opening  of 
the  valve  by  the  action  of  the  regulator,  or  by  insufficient  ports  and  passages. 
Such  a  diagram  may  do  fairly  at  115  revolutions  per  minute ;  what  would  it 
do  at  250  or  275,  the  usual  speed  of  the  engine  of  which  this  motion  is 
evidently  a  copy  I 


1 88 


TWENTY   YEAK8  WITH  THE  INDICATOR. 


LESSON  LXL 


EFFECT  OF  SPEED  ON  REALIZED  PRESSURE    IN    THE  CYLINDER— A 
LESSON  ON  FEED  PIPES. 

In  Figs.  123, 124,  \ve  have  valuable  information  in  reference  to  one  of  the 
most  important,  least-attended  to  details  of  steam  engineering.  Both  these 
diagrams  are  taken  from  the  same  engine,  under  the  same  conditions,  except 
with  reference  to  speed.  Fig.  123  is  from  the  engine  in  its  regular  work. 
Cylinder  diameter  34  inches,  stroke  60  inches,  revolutions  50  per  minute, 
boiler  pressure  69,  scale  40,  condensing.  We  find  62  pounds  of  initial  press- 
ure realized.  By  the  demonstration,  with  A  as  the  base  line,  we  find  the  cut- 
off at  D,  C.  The  theoretical  curve,  it  will  be  seen,  follows  the  expansion  line 
exactly,  covering  it  from  a  short  distance  beyond  the  line  D,  which  is  quite 
sufficient  for  the  purpose  of  demonstration,  showing  that  the  62  pounds  steam 


FIG.  123. 

pressure  cut-off  at  D,  would  make  precisely  the  expansion  line,  making  a  most 
effective  working  of  the  steam;  and  for  determination  of  the  one  point  of 
particular  interest  in  this  lesson,  viz.,  that  the  feed  pipe  in  this  case  was 
amply  sufficient  to  supply  that  engine  at  that  speed,  doing  that  amount  of 
work.  In  our  own  practice  we  would  prefer  to  have  had  the  exhaust  valve 
open  sooner,  as  at  F,  in  order  to  allow  the  condenser  to  sooner  realize  the 
vacuum.  In  this  case,  on  the  opening  of  the  valve,  about  four  pounds  is 
realized,  while,  were  the  valve  opened  slightly  earlier,  ten  pounds  ought  to 
have  been.  If  the  exhaust  valve  opened  sooner,  it  would  necessarily  close 
sooner,  and  we  should  have  an  approximation  of  the  compression  line  to  that 
of  G. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


189 


In  Fig.  124  we  have  the  same  engine  running  68  revolutions  per  minute 
for  some  especial  work  required ;  at  the  time  of  taking  the  diagram,  we  have 
73  pounds  of  boiler  pressure.  In  this  diagram,  124,  it  will  be  noticed  that 
the  admission  line  is  a  trifle  late,  the  initial  pressure  realized  is  72  on  the 
very  commencement  of  the  stroke,  or  before  the  piston  gets  into  motion; 
directly  the  motion  of  the  piston  commences  to  increase,  the  pressure  falls 

away  very  rapidly,  so  that  at  the 
point  of  cut-off  we  have  only  58 
pounds.  The  demonstration  in 
this  case  shows  that  the  pressure 
falls  very  rapidly  indeed,  from  the 
commencement  of  the  movement 
of  the  piston  until  at  the  point 
where  the  theoretical  curve  and 
the  actual  line  of  the  indicator 
touch,  just  above  the  letter  D; 
there  was  20  pounds  less  realized 
pressure  than  at  the  commence- 
ment of  the  stroke,  leaving  52 
pounds  effective  pressure  on  the 
piston  only. 

The  demonstration  in  this 
case,  made  from  the  point  A,  gives 
the  cut-off  on  the  line  C,  from 
which  the  theoretical  curve  is 
dropped,  exactly  following  the 
line  of  expansion  from  the  inter- 
section of  tho  two  lines  to  the 
point  which  is  the  base  of  the 
demonstration.  Upon  continuing 
this  line,  the  terminal  pressure 
will  be  found  slightly  above,  show  • 
ing  that  a  volume  of  steam,  equiv- 
alent to  the  full  pressure,  on  the 
line  C  up  to  the  line  between  B,  D, 
was  used  to  effect  this.  In  the 
case  of  this  movement,  we  find 
FIG.  134.  that  the  supply  pipe  for  this  en- 

gine,  which  was  sufficient  for  50 

revolutions,  is  entirely  insufficient  for  68  revolutions;  and  we  also  find 
another  feature  at  the  terminal  of  the  expansion  line,  viz.,  that  a  very  much 
less  vacuum  is  obtained,  and  none  at  all  until  after  the  piston  has  returned 
several  inches  on  its  stroke.  The  maximum  vacuum  is  ten  pounds ;  the  first 
quarter  of  the  stroke  eight  pounds  only  is  realized ;  the  second  quarter  nine, 
the  third  quarter  ten,  and  the  cushion  commences  on  ten  pounds.  Had 
the  exhaust  valve  been  timed  earlier,  as  recommended  for  123,  we  should 


190  TWENTY  YJSARS  WITH  THE  INDICATOR. 

have  obtained  the  dotted  line  E  or  some  approximation  to  it,  and  the  dotted 
line  F,  as  a  realized  vacuum,  which  would  have  added  materially  to  the  power 
of  the  engine  and  also  in  the  saving  of  steam.  Allowing  the  alteration  to 
have  been  made  in  the  time  of  the  exhaust  valve,  we  should  also  have  obtained 
the  compression  line  G  and  have  compressed  to  35  pounds,  saving  exactly 
this  amount  of  live  steam  in  opening  our  steam  valve  upon  35  pounds  instead 
of  nothing.  This  shows  the  necessity  of  a  proper  supply,  and  that  the  supply 
pipe  must  be  proportioned  to  the  speed  at  which  the  engine  will  travel,  and 
that  unless  this  is  done  some  such  change  in  matters  will  occur  as  that  shown. 
Should  123  call  for  a  much  larger  load,  the  supply  pipe  in  that  case  would  be 
insufficient,  for  it  must  be  understood  that  after  the  piston  goes  a  proportion 
of  the  stroke  in  its  travel,  it  calls  for  steam  very  much  faster  than  when  it  first 
starts.  In  this  case,  123,  the  pressure  is  somewhat  reduced,  and  if  the  engine 
were  required  to  carry  three  or  four  inches  further  we  should  probably  find,  in 
a  less  degree,  the  same  features  attending  the  steam  line  as  in  124. 


LESSON  LXII. 


ANOTHER  LESSON  ON   SUPPLY  PIPES. 

Changing  the  circumstances  as  much  as  possible  to  make  the  application 
more  forcible,  we  have  taken  Fig.  125  of  the  high-speed  class  of  engines  and 
running  under  fully  as  much  load  as  the  builders  recommend.  This  is  taken 
from  an  Armington  &  Sims,  14  J  inches  diameter  of  cylinder,  13  inches  stroke, 
running  245  revolutions  per  minute,  boiler  pressure  92  pounds,  scale  60,  in- 
dicating about  125  horse-power,  fed  with  a  six-inch  steam  pipe.  The  realized 
pressure  is  83  pounds,  the  steam  is  carried  150  feet  frpm  the  boilers  through 
several  elbows. 

The  demonstration  in  this  case  by  the  line  A,  parallels  B  B,  gives  the 
point  of  cut-off  at  B  C  (for  clearness  the  ordinate  is  not  drawn),  C  represents 
the  steam  line,  its  cut-off  is  very  sharp.  The  oscillations  in  this  diagram  are 
referred  to  in  previous  lessons,  and  the  point  of  cut-off  and  the  following  of 
the  theoretical  curve  is  through  the  intersecting  points  of  the  lines  d  d  which 
are  drawn  at  six  different  places  in  the  expansion  line.  It  will  be  seen  in  this 
case,  that  the  variations  in  the  line  of  expansion  of  the  instrument  vary  but 
very  slightly  from  the  actual  passage  of  the  theoretical  line,  and  this  approxi- 
mation is  so  close  that  the  drawing  of  the  theoretical  curve  would  simply  con- 


TWENTY  YEARS  WITH  THE  INDICATOR, 


191 


fuse.  The  commencement  of  release  at  the  point  E  compares  well  with  the 
compression  F,  but  if  anything  the  compression  is  slightly  larger  in  propor- 
tion to  the  stroke  than  the  release,  and  in  a  high  speed  engine  this  is  some- 
what a  necessity.  The  exhaust  line  varies  only  in  the  least  possible  degree 
from  the  atmospheric  line  of  the  instrument  until  the  exhaust  valve  closes  at 
F.  The  compression  line  has  the  same  wavy  appearance  that  the  expansion 
line  has,  but  exactly  reversed  in  effect.  We  have  a  compression  here  amount- 
ing to  60  pounds  when  the  steam  valve  opens  and  the  admission  line  is 
formed. 

The  amount  of  power  yielded  by  this  engine  is  large,  when  we  take  the 
volume  of  the  cylinder  into  consideration,  but  is  not  its  maximum  power  when 
we  take  its  speed  into  consideration.  The  admission  and  steam  lines  are  very 
square ;  the  cut-off  is  very  clearly  marked  and  all  the  lines  of  the  diagram 
give  a  high  efficiency,  which  has  since  been  proved  by  trial  of  the  engine,  and 
in  comparison  with  Figs.  123  and  124,  it  will  be  seen  that  a  very  large  pipe 
for  the  volume  of  the  cylinder  is  required  as  the  speed  is  increased.  The 
efficiency  of  Fig.  125  is  above  90  per  cent,  and  shows  good  sense  in  connec- 
tions, as  the  outline,  in  itself,  shows  very  satisfactory  work  with  the  steam  so 
far  as  valves  and  engine  are  concerned.  It  is  probably  in  three  cases  out  of 
five  that  we  find  too  small  feed  pipe,  and  in  entirely  too  many  cases  too  small 
exhaust  pipes  as  well.  Both  of  these  points  work  against  the  efficiency  of  the 
engine  and  whenever  efficiency  is  involved  then  economy  is  certainly  less  than 
it  should  be.  The  comparison  between  the  three  diagrams  123,  124,  125  will 
be  interesting  on  this  point  of  feed  pipes,  realized  or  lack  of  realized  pressure. 


FIG.  125. 


I92 


TWENTY  YEARS  WITH  THE  INDICATOR. 


LESSON  LXIH. 


LARGE  CYLINDER,  LOW-PRESSURE  ENGINE  ON  A  SOUND  STEAMER. 

Fig.  126  was  taken  from  the  steamer  Providence,  one  of  the  Old  Colony 
Steamboat  Company's  Sound  steamers,  running  between  New  York,  Newport 

and  Fall  River.  The  cylinder  is 
110  inches  in  diameter,  12  feet 
stroke,  and,  when  running  full, 
makes  17  revolutions  per  minute, 
scale  16,  steam  at  the  moment  of 
taking,  23  pounds. 

The    demonstration  has   been 
made  only  upon  one  diagram.     The 
admission  line  is  a  little  late  upon 
the   right  hand,  the  steam  line  is 
perfectly    satisfactory,  carrying  21 
pounds  almost  to  the  point  of  cut- 
off   and   cutting   off  at   barely  20 
pounds  pressure.     In  this  case  the 
demonstration  has  been  made  inside 
the  center  of  expansion  for  the  pur- 
pose of  putting  the  engine  to  a  dis- 
advantage, if  it  was   not  handling 
steam  correctly.     The  valve  closes 
at  D,  on  C;    the  line  C  has  been 
broken  to  prevent  a  confusion  with 
the  steam  line  of  the  diagram.     A 
few  inches  to  the  right  of  D  the 
valve   commences  to  close.     From 
the  time  the  valve   commences  to 
close  until  it  does  close,  the  piston 
only  travels  5f  inches.     The  expan- 
sion line   is  very  nearly  a  perfect 
one;  the   difference   is    so    exceed- 
ingly small  that  there  is   nothing 
in  practice  to  find  fault  with.     The 
release  might  be  improved  by  open- 
ing a  trifle  earlier.     The  condenser 

takes  hold  with  seven  pounds  and  runs  down  to  eleven  before  reaching 
half-stroke  and  to  almost  twelve  on  the  last  part  of  the  stroke.  If  the 
engine  released  a  trifle  earlier,  a  little  more  compression  would  be  the  re- 


\ 


41- 


\ 


/C3I 
/ 


FIG.  12(5. 


TWENTY  YEARS  WITH  THE  INDICATOR.  193 

suit,  and  if  the  compression  were  increased  slightly  we  believe  it  would  make 
the  engine  run  steadier,  but  this  matter  of  release,  vacuum  and  compression, 
is  so  entirely  a  part  of  the  engineer's  fancy,  that  so  long  as  the  engine  runs 
quiet,  they  do  not  mind  it,  and  so  few  of  them  are  furnished  with  indicators 
that  they  really  have  to  run  the  engine  by  their  eye  and  ear,  which  is  not 
exactly  to  the  credit  of  the  owners,  nor  in  all  cases  to  the  owner's  profit.  For 
some  unexplained  reason  there  is  a  difference  between  the  right  and  left-hand 
diagrams.  It  may  have  been  caused  by  a  little  variation  in  the  steam  press- 
ure between  the  times  of  taking  from  the  different  end  of  the  cylinder,  or 
what  is  much  more  likely  to  be  the  case,  the  bottom  or  left-hand  very  likely 
opens  the  valve  wider,  and  it  certainly  opens  it  a  trifle  sooner  than  the  top 
end  or  right-hand  diagram.  The  upper  line  represents  boiler  pressure  ;  the 
approximation  is  very  close  indeed  on  the  bottom,  and  the  amount  of  pressure 
realized  on  the  top  end  is  maintained  very  nicely,  and  for  that  reason  we  sup- 
pose it  must  be  that  the  valve  opens  a  trifle  late  and  does  not  open  fully. 
Practically  the  diagrams  are  very  fine. 

Few  people  have  any  real  idea  of  the  amount  of  power  involved  in  such 
diagrams.  Every  pound  of  mean  pressure  on  this  engine  at  the  speed  it  was 
running  at  the  time  these  diagrams  were  taken,  gives  117^  horse-power,  the 
piston  traveling  408  feet  per  minute  ;  figuring  these  diagrams,  we  find  the 
top  end  yields  2771.143  horse-power,  while  the  bottom  end  gives  2747.209 
horse-power ;  a  little  difference  in  the  ends  makes  a  very  large  difference  in 
horse-power,  and  also  makes  a  very  considerable  difference  in  the  economy  of 
the  run.  We  have  no  data  to  give  us  the  exact  coal  consumption  of  this  ship. 
The  release  on  the  bottom  at  E  is  hardly  as  good  as  upon  the  other  end  of 
the  cylinder,  the  realized  vacuum  at  F  being  eight  pounds  only.  The  engines 
of  the  Providence  are  fitted  with  the  Sickles  cut-off,  and  show  a  very  decided 
contrast  in  closing  with  those  using  the  rounded  wiper  cam,  and  decidedly  to 
the  advantage  of  the  engine. 


LESSON  LXIY. 


LARGE  LOW-PRESSURE  ENGINE.      ANOTHER  SOUND  STEAMER. 

Fig.  127  was  taken  from  the  new  steamer  Pilgrim  of  the  Old  Colony 
Steamboat  Company's  New  York  and  Fall  Eiver  Line,  after  she  had  been  run- 
ning a  few  months.  The  dimensions  of  her  engine  are,  cylinder  110  inches 
in  diameter,  length  of  stroke  14  feet,  speed  at  regular  duty  17  revolutions 
per  minute,  or  476  feet  of  piston  travel  per  minute ;  the  area  of  the  piston  is 


i94  TWENTY  YEARS  WITH  THE  INDICA  TOR, 

9503.34  inches,  giving  as  a  result  137. 078  horse-power  for  each  pound  of  mean 
pressure.  The  diagram  is  taken  with  a  24  spring. 

The  line  C  represents  boiler  pressure  at  the  moment  of  taking,  which  is 
43  pounds.  The  demonstration  in  this  case  is  made  on  the  bottom  end,  from 
the  base  line  A,  using  the  parallels  B  B,  showing  the  point  of  cut-off  on  C, 
at  the  intersection  of  C  D.  The  expansion  line,  it  will  be  noticed,  runs  down 
very  closely  to  the  actual  line  of  the  instrument  after  the  valve  gets  entirely 
closed.  That  there  may  be  no  misunderstanding  with  reference  to  the  line 
D,  it  may  be  explained  that  the  intersection  of  D  with  C  shows  where  the 
realized  pressure  should  have  been  cut  off  to  produce  the  amount  of  power 
from  the  pressure  at  the  point  A.  As  a  matter  of  fact  the  steam  valve  did  not 
close  at  the  line  D,  for  the  pressure,  it  will  be  seen,  drops  away  six  pounds 
between  the  line  C  wrhich  is  realized  pressure,  and  the  dotted  line  of  the  in- 
dicator, showing  the  difference  between  the  indicated  pressure  and  the  boiler 
pressure  at  that  point  of  six  pounds.  After  the  piston  passes  this  point,  the 
diagram  plainly  shows  that  more  steam  entered  the  cylinder,  so  that  the 
volume  which  entered  was  sufficient,  had  the  pressure  been  realized,  to  have 
equaled  the  effect  of  the  full  pressure  of  43  pounds,  cut  off  at  the  intersection 
of  CD. 

We  think  the  valves  of  this  engine  might  be  improved  with  profit  to  its 
owners.  To  get  an  idea  of  the  distances  represented  by  these  indicator  lines, 
the  release  opens  on  the  bottom  end,  expansion  line,  eight  inches  before  the 
piston  gets  to  the  end  of  the  stroke,  and  if  it  opened  still  sooner  it  would  be 
better,  for  after  the  piston  passes  the  center,  we  only  realize  about  four  pounds 
of  vacuum,  and  this  is  increased  until  ten  pounds  is  realized.  When  a  pound 
of  mean  pressure  means  almost  150  horse-power,  every  pound  of  the  vacuum 
has  a  value  in  dollars  and  cents  worth  looking  after.  If  the  release  of  this 
engine  could  be  made  slightly  quicker,  say  ten  or  twelve  inches,  so  as  to  be 
wide  open  by  the  time  the  cylinder  reaches  the  center  or  extreme  limit  of  the 
stroke,  then  the  condenser  would  sooner  get  hold,  and  gave  a  greater  effect 
for  vacuum.  The  exhaust  valve  commences  to  close  so  that  compression 
begins  25  inches  before  the  piston  reaches  the  bottom  of  the  cylinder.  In 
taking  steam,  notice  the  rounded  corner  where  the  admission  runs  into  the 
steam  line ;  but  this  very  slight  difference  on  this  engine  means  3f  inches  that 
the  piston  moves  before  the  steam  reaches  the  highest  point  in  the  cylinder. 
We  have  now  42  pounds  of  initial  realized,  while  at  the  point  of  cut-off  from 
the  demonstration  we  have  only  36,  terminal  pressure  at  the  commencement  of 
release  is  ten  pounds  above  atmospheric.  This  valve  is  slow  in  its  opening 
and  most  decidedly  too  slow  in  its  closing,  with  regard,  at  least,  for  the  engine 
or  the  economical  handling  of  the  steam. 

The  top  diagram  we  have  made  no  demonstration  from,  leaving  it  with- 
out any  confusion  of  lines  for  a  close  study,  and  it  has  some  points  of  superi- 
ority over  that  of  the  bottom.  Its  admission  and  steam  lines  are  decidedly 
better  ;  the  release  is  not  quite  as  quick,  and  the  compression  is  not  quite  as 
much.  Excepting  the  steam  valve  on  the  top  end,  all  the  valves  of  this  engine 
could  be  quickened  with  benefit  to  it  and  its  work.  To  get  a  proper  idea  of 


TWENTY  YEARS  WITH  THE  INDICATOR. 


195 


the  advantage  of  handling  these  valves  correctly,  we  have  only  to  refer  to  the 
amount  of  power  shown  by  the  diagram  in  Fig.  127.  The  bottom  end  shows 
4935.679  indicated  horse-power,  while  the  top  end  taken  with  an  intermission 
of  one  minute  or  two,  shows  4443.479  horse-power.  When  we  come  to  handle 

5,000  horse-power  of  steam  in  a 
single  cylinder  and  with  a  single 
steam  and  exhaust  valve,  it  be- 
comes very  necessary  to  be  careful 
in  the  adjustment,  not  only  for 
the  economy  of  steam,  but  as  well 
for  the  wear  and  tear  of  the  en- 
gine. Compare  Fig.  127  with 
Fig.  126  ;  the  steamer  Providence 
makes  the  best  use  of  steam,  being 
fitted  with  the  Sickles  cut-off  and 
the  Pilgrim  with  the  Stevens. 
These  cylinders  are  very  large  and 
the  more  perfect  the  adjustment 
of  the  valves,  the  finer  work  and 
consequently  higher  grade  of  econ- 
omy will  be  produced.  All  these 
engines  are  fitted  with  the  old- 
fashioned  side-pipe,  indicator  cock 
in  the  middle,  and  we  hope  some 
day  steam  engineers  will  progress 
out  of  this  absurd,  incorrect  and 
misleading  notion.  The  day  has 
gone  by,  when  the  width  of  a 
man's  thumb  will  do  in  adjusting 
steam  machinery,  and  the  interval 
of  time  on  an  engine  making  only 
17  revolutions  per  minute,  or  476 
feet  of  piston  speed  in  that  min- 
ute, which  is  required  for  the 
steam  to  pass  through  into  the 
indicator,  is  quite  misleading  as  to 
the  actual  position  of  the  valves.  Compare  Figs.  116  and  117,  on  a  small, 
quick-running  engine,  notice  the  difference  in  position  between  the  three-way 
cock  and  the  direct  attachment,  and  multiply  that  difference  by  the  difference 
between  the  14-inch  cylinder  and  the  14-feet  cylinder,  running  17  revolutions 
instead  of  about  225.  In  all  these  steamship  diagrams,  it  has  been  absolutely 
impossible  to  get  a  short  connection  with  the  end  of  the  cylinder,  so  as  to  show 
the  actual  position  of  the  valves. 


FIG. 


TWENTY  YEARS  WITH  THE  INDICATOR 


LESSON   LXV. 


AN    OVERLOADED    ENGINE. 

Fig.  128  was  taken  from  a  Buckeye  engine  in  the  wire  mills  of  a  large 
steel  works.  Diameter  of  cylinder  is  16  inches,  stroke  32  inches,  95  revolu- 
tions per  minute,  100  pounds  boiler  pressure,  scale  60,  indicating  2404- 
horse-power. 

There  are  only  two  objects  to  be  attained  by  showing  such  a  diagram  as 
Fig.  128 ;  the  first  is  to  show  the  excellent  handling  of  the  steam  by  the 
valves  on  an  engine  indicating  90  per  cent,  more  than  it  was  ever  intended  by 


Fm.  128. 

the  builders,  taking  the  rating  of  the  engine  at  125  horse-power  and  adding  90 
per  cent,  to  it ;  the  other  reason  is  to  show  how  extremely  inconsistent  the 
owners  of  steam  engines  are  in  asking  a  load  equivalent  to  almost  double  its 
rated  power.  Out  of  a  hundred  pounds  boiler  pressure,  the  engine  has  an 
initial  realized  pressure  of  96  pounds,  cutting  off  between  95  and  96  pounds 
pressure  at  the  actual  point  of  cut-off  from  the  demonstration.  The  theo- 
retical curve  in  this  case  follows  the  expansion  line  almost  exactly,  and  it  is  a 
wonder  how  the  engine  relieves  itself  in  exhausting  from  a  terminal  pressure 
of  46  pounds  above  the  atmosphere,  and  yet  the  engine  exhausts  with  a  back 
pressure  of  about  two  pounds.  The  terminal  pressure  is  almost  exactly 
identical  on  both  ends ;  there  is  an  extremely  small  variation  by  the  planim- 
eter  in  the  area  of  the  two  ends,  and  taken  all  in  all,  it  may  be  considered  as 
a  first-class  accomplishment  in  doing  such  a  large  amount  of  power.  It  is  a 
credit  k>  the  builders,  but  no  credit  whatever  to  the  owners  of  the  machine 
who  will  abuse  a  good  engine  like  this. 


TWENTY   YEARS  WITH  THE  INDICATOR. 


197 


The  practice  of  overloading  is  becoming  too  common.  A  number  of  very 
bad  accidents  have  occurred  within  the  past  few  months,  and  steam  engine  users 
may  by-and-by  become  accustomed  to  the  rational  use  of  an  engine  and  the 
proper  care  of  it  as  well. 


LESSON  LXVL 


HARRIS-CORLISS  ENGINE,    OVERLOADED— FINE  CARD. 

Fig.  129  is  taken  from  one  of  a  pair  of  Harris-Corliss  engines,  running-  in 
the  Exposition  Cotton  Mills,  in  Atlanta,  Ga.     Some  repairs  had  to  be  made 


FIG.  129. 

upon  one  side,  and  the  other  side  in  producing  this  diagram,  drove  the  fol- 
lowing amount  of  machinery:  4  pickers,  99  cards,  288  slubber  spindles, 
1,320  fine  speeder  spindles,  11,400  spinning  frame  spindles,  306  looms,  six 
spoolers,  four  warpers,  with  brusher,  folder  and  press.  The  size  of  the 
engine  is  24x48,  speed  77  revolutions  per  minute,  scale  40,  boiler  press- 
ure 83. 

The  production  of  this  diagram  is  a  credit  to  the  engineer  in  charge,  as 
well  as  to  its  builder.  The  engines  had  been  in  operation  for  nearly  three 
years  at  the  time  this  card  was  taken.  It  will  be  seen  that  the  steam  press- 


198  TWENTY  YEARS  WITH  THE  INDICATOR, 

ure  realized  is  fully  up  to  boiler  pressure  ;  the  credit  of  this  is  due  to  the 
fact  that  new  steam  pipes  have  been  put  on  by  the  present  agent,  and  the 
engines  are  not  at  all  throttled.  The  engine  in  this  case  is  doing  about  two- 
thirds  of  the  work  of  the  mill  with  one  side,  and  is  starting  with  83  pounds 
of  realized  pressure,  the  cut-off  closes  on  77  pounds,  showing  that  the  extra- 
ordinary demand  for  steam  is  much  better  met  than  in  the  average  supply 
pipe,  or  that  the  capacity  of  the  feed  pipe  is  fully  up  to  a  large  increase  of 
load  over  the  regular  power  of  the  engine,  when  both  sides  and  its  regular 
load  are  running.  The  expansion  line  by  the  demonstration  shows  but  an 
exceedingly  trifling  variation  at  that  point,  and  the  terminal  pressure  is  almost 
absolutely  correct.  A  little  earlier  release  would,  perhaps,  avoid  the  small 
amount  of  back  pressure  shown.  The  compression  is  sufficient  to  keep  the 
engine  working  smoothly  and  the  steam  line  is  practically  correct. 

This  is  as  fine  a  diagram  as  we  may  expect  from  practice,  and  in  this 
particular  case  the  engineer  of  the  mills  has  given  a  great  deal  of  attention 
to  the  adjustment  of  valves  by  the  indicator,  wrhich  has  been  backed  up  by  a 
good  mechanical  knowledge  and  ability,  as  well  as  good  common  sense.  The 
horse-power  is  390.2509.  This  is  another  case  of  overloading  by  reason  of 
necessity,  but  it  is  not  in  excess  of  the  ability  of  the  engine  to  do  it  very 
economically,  and  correctly  as  well.  The  ends  of  the  engine  vary  less  than 
one  horse-power  in  total  amount  of  load. 


LESSON  LXVH. 


THE  LATEST  TRIPLE  COMPOUND  STEAM  ENGINE. 

The  diagrams  in  this  lesson  are  from  one  of  the  latest  specimens  of 
marine,  triple  compound  engines,  having  a  high-pressure  cylinder  in  the  center 
with  a  compound  fore  and  aft.  The  high-pressure  cylinder  is  71  inches 
diameter,  six  feet  stroke,  running  70  revolutions  per  minute,  boiler  pressure 
110,  scale  40.  Fig.  130  is  from  the  high-pressure  cylinder,  in  which  J,  I, 
represent  respectively  the  base  line  of  our  demonstration  for  the  top  and 
bottom  diagrams  respectively.  The  line  C  is  that  of  initial  or  realized  press- 
ure, D  is  the  line  of  boiler  pressure,  A,  B  are  respectively  the  points  of  cut- 
off, A  for  the  top  cylinder,  B  for  the  bottom,  their  intersection  with  the  line 
C,  marking  the  point  at  which  realized  pressure  was  cut  off  practically,  to  oc- 
complish  the  pressure  at  J,  I,  respectively,  at  that  point  in  the  stroke.  The 


TWENTY  YEARS  WITH  THE  INDICA  TOE. 


199 


top  diagram  of  this  engine  is  somewhat  peculiar,  and  the  line  A,  which  is, 
properly  speaking,  tlie  volume  of  steam  from  H  to  A,  which  was  used  in  the 
bottom  of  the  cylinder,  is  in  this  case  used  to  show  where  the  valve  was  sup- 
posed to  cut  off  from  the  staff  of  the  engine  ;  it  is  found  by  the  demonstration 
to  be  entirely  misleading,  as  the  terminal  pressure  is  12  pounds  below  the 
real  theoretical  line,  or  below  the  actual  point  of  cut-off  from  the  steam  con- 
sumed. The  line  A  then  becomes  the  volume  of  the  cylinder  from  H  to  A, 
which  was  actually  used  at  the  initial  pressure  C  to  accomplish  the  result 
which  is  given  by  the  actual  line  of  the  instrument,  the  steam  and  expansion 
lines  of  which  are  shown  by  dotted  lines.  The  motion  of  the  valve  is  a  little 
late  in  admission  on  both  ends,  the  bottom  carries  steam  farthest  and  ac- 


FIG.  130. 

complishes  the  most  work,  the  top  end  cylinder's  pressure  falls  off  more  than 
in  the  case  of  the  bottom,  and  the  actual  line  of  expansion  from  B,  C  shows  a 
near  approximation  to  the  line  of  the  instrument  on  its  expansion  from  the 
time  when  the  two  lines  run  on  nearly  together ;  on  the  bottom  end  the  line 
approximates  reasonably  close.  But  what  shall  we  say  to  the  loss  of  press- 
ure, which  is  13  pounds  between  the  initial  and  the  boiler  pressure,  and  10 
pounds  between  initial  and  the  line  of  the  indicator  at  the  point  of  cut-off,  or 
23  pounds  below  the  boiler  pressure  at  the  point  of  cut-off  on  the  top  ;  on  the 
bottom  end  30  pounds  is  lost  from  boiler  pressure  and  17  from  initial  press- 
ure at  the  point  of  cut-off.  The  average  pressure  in  the  receiver  from  the 
high-pressure  cylinder  is  from  22  to  24  pounds  above  the  atmosphere.  The 
power  developed  by  the  bottom  is  5449.5  horse-power,  by  the  top  5054.61 


200 


TWENTY  YEARS  WITH  THE  INDICATOR. 


horse-power,  taking  the  actual  line  of  the  indicator.  If  this  cylinder  had  cut 
off  boiler  pressure  at  the  intersection  of  the  two  lines  with  D,  it  would  have 
added  to  the  bottom,  all  other  being  the  same,  1184.675  horse-power,  with  the 
same  expenditure  of  steam,  and  to  the  top  would  have  added  1693.64  horse- 
power. This  gives  then  an  idea  of  the  efficiency  of  the  engine.  The  release 

is  excellent,  and  we  have  some  doubts 
as  to  the  exact  accuracy  of  these 
diagrams  from  several  minor  points, 
and  we  believe  the  conditions  under 
which  the  engine  is  working  would 
be  more  reliably  shown  by  an  un- 
proved indicator ;  these  are  the  same 
features  shown  in  a  previous  lesson, 
where  a  contrast  is  shown  as  between 
the  old-fashioned  instrument  and  the 
new  Thompson. 

Fig.  131  is  taken  from  the  for- 
ward low-pressure  cylinder  105  inch- 
es in  diameter,  six  feet  stroke,  70 
revolutions,  spring  16.  In  this  case, 
D  represents  the  receiver  pressure 
from  the  atmospheric  line  23  pounds ; 
the  top  end  of  this  cylinder  real- 
izes 17^  pounds,  which  falls  off  at  the 
point  of  cut-off  to  15,  while  the  bot- 
tom end  only  realizes  16  pounds, 
falling  off  at  the  point  of  cut-off  to 
15.  Both  ends  of  this  cylinder  real- 
ize much  better  than  the  average 
low-pressure  on  the  compound ;  ow- 
ing to  this  the  vacuum  falls  to  ten 
pounds  at  one-fifth  stroke  and  to  1*3 
pounds  at  the  end  of  the  stroke,  or 
before  the  exhaust  valve  is  closed. 
A,  A'  are  the  base  lines.  B  is  the 
point  of  cut-off  on  line  of  realized 
pressure  for  the  top,  B'  for  the  bot- 
tom end  of  the  cylinder.  The  bot- 
tom end  shows  4102.98  horse-power,  the  top  end  shows  4401.92  horse- 
power,  with  a  very  considerable  loss  between  the  realized  pressure  and 
the  pressure  in  the  receiver  as  shown  by  the  high-pressure  diagram. 

Fig.  132  is  from  the  aft  low-pressure  of  compound,  cylinder  same  size  as 
the  forward  cylinder,  same  scale.  This  cylinder  for  some  reason  shows  a  very 
considerable  increase  of  power  and  a  much  better  realization  of  receiver-press- 
ure on  the  top  end  than  on  the  bottom,  as  the  top  end,  when  the  valve  is  fully 
open,  realizes  22£  pounds,  the  bottom  end  only  19J.  The  steam  valve  for  the 


FIG. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


201 


bottom  end  of  this  cylinder  is  considerably  later  than  the  steam  valve  for  the 
top  end.  The  point  at  which  steam  was  cut  off  is  a  little  longer  on  the  bottom 
than  on  the  top,  but  the  top  end  of  the  cylinder  makes  the  best  use  of  the 
steam.  The  release  in  this  case  is  early,  so  that  a  good  vacuum  is  obtained  at 
the  very  commencement  of  the  stroke,  which  is  held  all  the  way  through.  A 

very  considerable  loss  is  made  as 
between  the  realized  and  theoret- 
ical from  the  pressure  at  A,  A', 
which  would  amount  to  some  hun- 
dreds of  horse-power.  The  dia- 
gram from  the  top  of  this  cylinder 
gives  4675.25  horse-power,  from 
the  bottom  4528.68. 

There  is  one  point  with  refer- 
ence to  the  compound  cylinders 
that  must  be  noticed :  the  practice 
is  becoming  very  common  of  run- 
ning the  low-pressure  with  the 
highest  vacuum  that  can  be  ob- 
tained. In  this  case  the  tempera- 
ture runs  from  236°  to  about  120°, 
and  it  is  fair  to  suppose  that  a 
certain  amount  of  condensation  is 
effected  every  time  the  cylinder  is 
filled  with  steam  after  having  ex- 
hausted through  the  condenser. 
There  may  be  serious  questions  as 
to  the  real  efficiency  of  the  com- 
pound engine  carried  to  an  ex- 
treme ;  and  undoubtedly  there  is 
a  serious  lack  of  economy  in  work- 
ing steam  as  these  three  diagrams 
show,  as  compared  with  the  ex- 
pense of  maintenance,  and  we 
doubt  somewhat  whether  this  style 
of  engine  will  very  long  continue. 
FIG.  132.  The  power  given  out  by  the  boilers 

in  the  high-pressure  cylinder,  in- 
cluding the  loss  in  handling  the  steam  and  the  resistance  in  the  receiver,  is  al- 
most 9,000-horse  on  each  end.  That  which  is  used  in  the  compound  cylinders 
makes  up  a  large  volume,  and  the  condenser  increases  the  amount  realized,  but 
whether  this  cannot  be  done  by  some  other  combination  is  a  question  which  we 
believe  engineers  shall  soon  study,  and  that  the  key  for  successfully  running  a 
large  ship  which  requires  from  12,000  to  14,000  horse-power,  as  does  this  one, 
lies  in  changing  the  proportion  of  the  compound  engine  materially  as  between 
the  different  cylinders,  and  realizing  more  heat  units  with  less  refrigeration. 


202  TWENTY  YEARS  WITH  THE  INDICATOR. 

There  must  be  a  way  of  using  steam  much  more  economically  than  is  shown 
by  these  figures,  which  are  from  one  of  the  very  latest  of  marine  engines  that 
have  not  yet  made  their  full  record  for  economy  or  speed,  but  which  have 
shown  a  very  large  power  ;  we  have  not  been  able  to  ascertain  the  relative 
efficiency  or  the  actual  economy  when  measured  by  pounds  of  coal. 


LESSON  LXVHI. 


GERMAN  BUILT   CORLISS  COMPOUND   ENGINE. 

Figs.  133  and  134  were  taken  from  a  Corliss  compound  engine  built  by 
the  Augsburg  Engine  Company,  Augsburg,  Germany,  at  work  in  a  spinning 
mill  in  that  neighborhood.  The  information  is  from  a  series  of  experiments 
made  by  Prof.  Schroter  of  Munich,  but  the  diagrams  which  we  illustrate  we 
obtained  direct  from  the  director  of  the  company  which  built  the  engine ;  no 
tracings  were  made  use  of,  but  original  diagrams.  The  engine  has  horizontal 
cranks  at  right  angles,  fitted  with  a  Sulzer  valve  gear,  having  a  horizontal  in- 
termediate receiver  placed  below  the  cylinders  and  at  right  angles  to  them. 
The  high -pressure  cylinder  is  jacketed  with  live  steam  from  the  boiler  to  the 
admission  valves.  The  low-pressure  cylinder  jacket  is  supplied  by  a  branch 
pipe  from  the  main  steam-pipe,  the  high-pressure  cylinder  cannot  be  shut  off 
but  the  low-pressure  can.  The  expansion  in  the  small  or  high-pressure 
cylinder  is  regulated  by  the  governor,  while  the  point  of  cut-off  in  the  low- 
pressure  cylinder  is  adjusted  to  any  varying  point  by  hand.  The  air-pump 
is  a  horizontal,  driven  by  bell-crank  below  the  engine-room  floor.  The  diameter 
of  the  small  cylinder  reduced  to  inches,  is  14.57  ;  large  cylinder  24.07  ;  pro- 
portion of  cylinders  l:2f  ;  clearance  of  the  high-pressure  cylinder  4.3  per  cent.* 
clearance  of  the  low-pressure  cylinder  3.1  per  cent.;  volume  of  receiver  ex- 
clusive of  clearance  11.548  cubic  feet ;  volume  of  the  receiver  to  the  volume  of 
the  low-pressure  cylinder  1:1.19;  revolutions  per  minute  71.29  ;  mean  piston 
velocity  444.5  feet;  stroke  37.4  inches.  Reducing  motions  were  used,  made 
of  pulleys,  fixed  at  either  end  of  the  guide  opening  in  the  frame,  on  the  hub 
of  which  a  small  drum  was  placed  to  give  the  indicator  barrel  proper  motion. 

The  professor  in  charge  of  the  test  remarks  that  when  the  valve  gear  of 
steam  engines  are  so  arranged  as  to  prevent  a  loss  of  pressure,  he  finds  an 
increased  economy  of  twelve  per  cent,  in  the  result,  and  this  was  taken  from 
two  pairs  of  engines  indicating  about  300  horse-power,  and  his  basis  is  made 


TWENTY  YEARS  WITH  THE  INDICATOR. 


20' 


V 


\ 


from  an  actual  test  instead  of  any  theoretical  comparison.  The  deduction  is 
also  brought  out  that  when  the  change  of  volume  between  the  receiver  and 
the  low-pressure  cylinder  ranges  from  0.2  to  1.2  times  the  volume  of  the  large 
cylinder,  that  a  mean  volume  of  receiver  equal  to  that  of  the  low-pressure 
cylinder  is  the  most  advantageous.  In  the  original,  the  metric  system  is  used 

in   all    dimensions   giving 
us   fractions   of   inches. 

Diagram  133  on,  as  near- 
ly as  practicable,  a  32  scale, 
shows  a  rather  handsome 
compression,  good  admis- 
sion, a  peculiar  little  jog  in 
the  commencement  of  the 
steam  line,  but  the  realized 
pressure  starts  off  at  eighty 
pounds,  closes  on  the  line 
B  with  70  pounds.  The 
expansion  line,  based  upon 
the  pressure  at  the  line  A, 
follows  very  closely  indeed 
until  past  the  middle  of 
the  stroke,  when  the  indica- 
ted pressure  expansion  line 
slightly  exceeds  the  theo- 
retical or  broken  line.  The 
terminal  pressure  is  about 
the  limit  of  expansion,  and 
the  receiver  gives  a  press- 
ure of  9  pounds  to  the 
square  inch  in  the  exhaust 
at  the  commencement  of 
the  stroke,  which  increases 
to  about  11  pounds  at  the 
middle  of  the  stroke,  and 
this  pressure  is  very  near- 
ly continued  to  the  com- 
mencement of  compres- 
sion. Taking  the  low 
pressure  cylinder  on  Fig.  134,  its  tarts  off  with  a  realized  pressure  of  10  pounds ; 
basing  our  demonstration  on  the  pressure  at  the  line  A,  we  find  the  cut-off 
to  be  at  the  intersection  of  E  B,  at  which  point  the  pressure  has  fallen  about 
three  pounds.  The  theoretical  and  the  actual  lines  run  on  very  nearly  togeth- 
er, showing  remarkable  efficiency  of  the  expansion,  but  a  considerable  loss  is 
realized  from  the  receiver  of  the  pressure  given  out  by  the  receiver.  The 
vacuum  realized  is  11  pounds  at  almost  the  commencement,  and  nearly  12 
pounds  at  the  commencement  of  compression. 


FIG.  133. 


2O4 


TWENTY  YEARS  WITH  THE  INDICATOR. 


We  may  judge  from  these  diagrams  that  the  efficiency  of  the  live  steam 
jacket  is  very  considerable,  and  yet  the  same  argument  as  in  the  case  of  the 
large  compounds  comes  up  in  this  question,  the  outside  of  the  cylinder  is 
heated  with  live  steam  and  the  inside  is  changed  a  hundred  degrees  or  more 
by  the  difference  between  the  realized  steam  pressure  and  the  vacuum  ob- 
tained at  each  stroke.  There  is  a 
somewhat  curious  theory  advanced  in 
the  lengthy  report  originally  made 
upon  this  engine,  which  is  embodied 
in  the  following,  referring  to  the  exact 
proportion  as  indicated  by  two  differ- 
ent diagrams :  "a  phenomenon  which 
goes  far  to  disprove  the  necessity  for 
employing  complicated  steam- distribu- 
tion apparatus  to  attain  nice  lines  in 
diagrams  ;  and  that  the  day  is  not  far 
distant  when  a  good  distribution,  by 
means  of  slide  valves,  will  be  preferred 
to  any  of  the  modern  forms  of  releas- 
ing gears." 

The  illustrations  Figs.  133,  134, 
show  us  distinctly  that  there  is  not 
that  perfection  attained  in  this  so- 
called  Corliss  engine  with  some  other 
kind  of  a  valve  gear,  as  will  be  found 
by  the  simple  Harris-Corliss  in  Fig. 
129,  or  the  Corliss  modern  compound 
in  Figs.  114,  115.  The  fact  will  not 
have  passed  from  the  engineering  fra- 
ternity who  are  familiar  with  steam 
engines,  that  slide-valve  gears,  which 
have  given  the  utmost  perfection  at- 
tainable in  the  nice  indicator  diagram 
lines,  lately  existed  in  the  United 
States,  but  that  these  engines  never 
showed  an  economy  to  compare  with 
the  Corliss,  when  economy  of  fuel,  the 
minimum  of  repairs  and  the  maximum 
of  durability  were  all  three  items  con- 
sidered, and  in  this  combination  the  Corliss  valve  gear,  up  to  a  reasonably 
high  speed  and  even  in  marine  service,  when  properly  cared  for,  has  out- 
stripped every  system  of  valves  that  has  so  far  been  applied,  while  the 
slide-valve  gear  referred  to  has  passed  out  of  use  commercially.  The  feed 
water  per  hour  as  given  in  this  report,  with  a  steam  jacket  in  use,  is  14.704 
pounds  of  feed  water  per  hour,  per  indicated  horse-power,  but  many  facts 
embodied  in  American  tests  are  not  reported.  Some  changes  were  made  in 


00  J 


FIG.  134. 


T  WENT?  YEARS  WITH  THE  INDIGA  TOR.  205 

the  volume  in  the  receiver  which  are  unimportant  here.  Taken  all  in  all  the 
diagrams  show  very  good  working  of  steam,  but  nothing  which  would  induce 
us  to  abandon  the  Corliss  valves,  or  prefer  the  suggestion  in  the  report  upon 
them,  of  the  adoption  of  the  slide-valve  in  preference  to  the  liberating  valve 
gear. 


LESSON  LXIX. 


MISTAKE  IN  THE  MOTION— RESULT. 

Fig.  135  shows  a  result  not  to  be  desired.  This  was  taken  from  an 
Armington  &  Sims  engine,  where  the  parties  had  trouble,  and  the  trouble  was 
in  getting  more  pressure  in  the  cylinder  than  they  had  in  the  boiler,  a  con- 
sequent reaction  which  was  not  particularly  desirable.  A  is  the  base  line  of 
the  demonstration,  B  the  volume  of  cylinder  filled,  E  boiler  pressure,  80 
pounds,  scale  40,  C  atmospheric  line,  D  absolute  vacuum,  theoretical  line  J. 
The  release  in  the  diagram  takes  place  a  little  before  letter  J,  and  directly 
under  J  the  expansion  line  crosses  or  falls  under  that  of  the  return  of  the  ex- 
haust which  is  slightly  above  atmospheric  pressure.  The  valve  apparently 
begins  to  close  at  about  half  stroke  on  the  exhaust,  carrying  the  compression 
up  very  rapidly,  and  at  the  point  F  the  compression  crosses  the  line  of  boiler 
pressure  passing  up  to  G  which  is  15  pounds  above  boiler  pressure.  Here 
the  amount  of  pressure  does  not  increase  any  further,  but  the  piston  continues 
its  travel  to  H,  at  H  at  the  end  of  the  travel  of  the  piston,  the  pressure  falls 
to  I,  where  the  steam  valve  evidently  commences  to  open,  and  allows  the 
pressure  to  pass  out,  or  to  equalize  itself  in  such  a  way  that  the  steam  line  is 
not  shown  as  it  ordinarily  is  made  by  this  engine. 

It  will  be  seen  at  the  very  outset,  the  point  of  cut-off,  B  E,  by  the  demon- 
stration, is  practically  inside  of  the  real  line  of  the  instrument,  but  only  for  a 
very  little  way.  The  theoretical  line  K  passes  through  the  line  of  the  instru- 
ment at  a  trifling  advance  beyond  the  line  B,  falling  below  it,  while  before  we 
reach  the  demonstration  line  A,  the  theoretical  line  is  above  the  actual  line  of 
the  indicator.  It  then  passes  below  it  before  the  release,  after  release  it 
barely  touches  the  expansion  line  on  its  return. 

This  is  a  very  curious  diagram,  for  the  readings  are,  to  a  certain  extent, 
negative  in  every  direction.  What  was  the  reason  ?  At  the  left  of  the  diagram 
we  have  drawn  the  whole  cause  of  the  trouble.  These  makers  use  a  pendulum 
with  an  arc  of  a  circle  from  which  the  cord  is  led  direct  to  the  indicator.  In 


206 


TWENTY  YEARS  WITH  THE  INDICATOR. 


this  case,  we  found  the  arc  of  the  circle  reversed,  or  the  upper  dotted  line  in- 
stead of  the  lower  shaded  line,  the  point  L  being  in  either  case  the  pulley  which 
received  the  cord  from  the  motion.  There  is  not  a  single  correct  line  on  the 
diagram  ;  the  motion  is  distorted  precisely  in  proportion  to  the  reversing  the 
arc  of  a  circle,  as  shown,  M  being  the  center,  the  cord  being  led  in  the  angle 
of  the  dotted  line  instead  of,  as  it  should  have  been,  from  below  M  or  the 
shaded  portion. 

Upon  adjusting  the  motion  the  diagram  assumed  its  normal  appearance, 
and  entirely  different  from  that  which  is  shown.  The  question  may  arise  in 
figuring  such  a  diagram  as  this  by  the  pianimeter,  what  to  measure,  from  the 
fact  that  there  are  negative  quantities  at  each  end  of  the  diagram.  We  have 


i5~H\ 


FIG.  135. 

therefore  drawn  two  arrows,  one  on  the  expansion  and  one  on  the  compression 
line,  to  show  the  direction  which  should  be  taken.  Locate  the  pianimeter 
properly,  start  at  the  intersection  of  the  line  at  F,  follow  the  line  in  the  same 
direction  that  the  pencil  of  the  indicator  followed  it ;  starting  at  F  follow  the 
steam  line  down  the  expansion  line  in  the  direction  of  the  arrow,  at  J  cross 
the  expansion  line,  come  up,  again  recross  the  expansion  line  under  J,  follow 
the  exhaust  and  compression  line  in  the  direction  of  the  arrow,  cross  F  up  to 
G,  to  the  right  to  H,  down  to  I,  then  down  to  F.  This  will  give  you  the 
area  less  the  negative  quantities  or  resistance.  Now  as  the  negative  quantities 
increase  the  length  of  the  diagram,  the  total  length  from  the  extreme  at  I  to 
the  other  end  at  the  left  of  J,  must  be  taken  into  the  account,  so  as  to  get  the 
correct  ordinate  which,  reduced  to  the  scale,  is  the  mean  pressure. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


207 


LESSON   LXX. 


DEFECTS  WHICH  ARE  SHOWN  BY  THE  INDICATOR.     COMPARISONS. 

The  various  adaptations  to  which  the  indicator  can  be  put,  the  certainty 
of  the  readings,  if  properly  interpreted,  the  different  defects  which  may  be 
pointed  out  with  absolute  certainty,  are  very  frequently  lost  sight  of,  more 
especially  when,  as  has  been  stated  in  this  volume  previously,  this  particular 
part  or  adjustment,  or  indications  for  defects,  has  been  kept  in  the  hands  of 
men  who  have  not  understood  it  any  too  well  themselves,  and  have  not  been 
fully  conversant  with  the  details  of  the  machinery  which  they  have  attempted 
to  criticise, 


FIG.  136. 

Take  Fig,  136,  and  taking  away  the  theoretical  dotted  line  D,  almost  any 
engineer  or  engine  builder  would  pronounce  it  a  very  fine-looking  card,  but 
the  purpose  of  this  volume  is  to  give  information.  We  must,  therefore, 
resort  to  our  demonstration,  and,  if  we  take  the  base  line  A,  the  scale  of  the 
diagram  being  30,  we  find  we  have  above  absolute  vacuum,  a  pressure  of  19 
pounds  plus.  Upon  making  the  demonstration,  we  are  rather  surprised  to 
find  that  the  point  of  cut-off  is  located  at  the  intersection  of  B,  C,  the  dis- 
tance from  the  left-hand  vertical  line  to  B,  representing  the  volume  of  the 
cylinder  in  comparison  to  the  whole  length  of  the  stroke,  which  was  filled 
with  steam  at  the  initial  pressure  of  40  pounds,  or  absolute  pressure  of  54 
plus. 

Taking  B  as  our  starting  point,  and  our  readers  must  not  forget  that 
these  are  two  different  problems  in  geometry,  the  first  problem  closes  with 
the  erection  of  the  point  B,  C,  we  then  adopt  the  second  problem,  which  is  to 
lay  out  the  hyperbolic  curve,  by  the  means  already  described ;  this  gives  us 


208  TWENTY  YEARS  WITH  THE  INDICATOR. 

the  long-dotted  line  D,  which  it  will  be  seen  starts  10  pounds  above 
the  actual  line  of  the  indicator  as  it  crosses  the  line  B,  gradually  near- 
ing  the  actual  line  of  the  indicator  at  A,  and  shortly  after  crossing 
below  the  actual  line  of  the  instrument.  We  find  that  the  end  of  the 
expansion  line,  which  is  under  the  atmospheric  line  is  three  pounds,  actual, 
above  the  theoretical,  or  13  pounds  above  the  absolute  vacuum,  instead  of  10 
as  it  should  be.  There  are  several  theoretical  questions  which  enter  into 
this,  that  it  is  not  our  purpose  to  discuss,  for  they  have  little  bearing  upon 
the  practicability  of  the  application  of  the  indicator  or  its  readings.  Our 
demonstration  is  based  upon  the  fact  that  the  expansion  line  in  the  cylinder 
is  entirely  settled  at  the  point  A,  or  about  half-stroke  on  the  expansion  ;  or, 
in  other  words,  that  it  is  less  liable  to  be  disturbed  here.  Now,  the  point  A 
is  a  positive  fact,  and  if  steam  expands,  according  to  Marriotte's  law,  or 
Regnault's  demonstration,  or  Joule's  experiments  (and  these  are  acknowledged 
as  approximate  to  the  fact)  then  the  actual  pressure  at  A  gives  the  point  B  C, 
as  where  the  initial  pressure  of  40  pounds  should  be  cut  off  and  expanded, 
according  to  these  different  authorities,  to  produce  the  pressure  at  A.  In 
this  case  the  point  A  is  higher  on  the  expansion  line  than  it  should  be  if  the 
steam  had  been  properly  cut  off  previous  to  B,  showing  that  something  must 
have  occurred  while  the  piston  traveled  from  B  to  A,  which  admitted  steam 
into  the  cylinder  after  the  cut-off  valve  closed,  as  is  shown  by  the  indicator 
line.  Now,  this  may  be  admitted  in  so  small  an  amount  as  to  apparently  be 
imperceptible,  and  the  demonstration  is  the  only  way  of  ascertaining  what 
does  occur.  In  this  case,  the  steam  was  admitted  after  the  cut-off  valve  ap- 
parently closes,  but  in  such  a  small  amount  that  at  A  it  is  sufficiently  high 
above  what  it  should  be,  to  throw  the  point  B  forward  on  the  line  C,  and  the 
other  end  of  the  expansion  line  quite  corroborates  this,  the  sequel  proves  the 
correctness  of  the  application.  When  the  engineer  who  submitted  the  dia- 
grams to  us,  was  allowed  an  opportunity  to  take  down  his  engine,  he  found  a 
bad  leak  under  the  steam  valve,  so  much  so  that  he  had  to  draw-file  the  end 
bearing  of  the  valve,  or  shoulders  of  the  valve,  to  let  down  upon  its  seat,  and 
to  stop  the  leak,  which  was  visible  when  the  cylinder  head  was  removed. 

The  old-fashioned  way  of  taking  the  terminal  pressure  and  working  back, 
would  be  a  very  wrong  practice  in  connection  with  this  diagram,  and  there 
need  not  be  any  confusion  in  the  minds  of  any  of  the  readers  of  this  work, 
who  correctly  apply  the  demonstration  to  any  diagram,  if  the  few  simple 
directions  are  followed  which  are  so  plainly  given.  It  will  at  once  settle  the 
fact,  that  something  is  wrong,  without  stopping  to  experiment. 

If,  now,  we  take  up  the  case  of  another  series  of  complications,  defects 
and  conditions  not  desirable,  we  will  refer  to  Fig.  137,  the  scale  of  which  is 
40,  steam  pressure  at  the  time  of  taking,  82  pounds.  This  was  a  new  engine 
built  to  run  83  revolutions,  and  was  sent  to  us  from  several  hundred  miles 
away.  The  actual  diagram  is  reproduced ;  A  representing  the  base  line  of  our 
computation,  B  the  point  of  cut-oft  at  which  the  initial  pressure  C  of  50 
pounds  was  equal  to  cutting  off  in  the  amount  of  steam  used  to  produce  the 
pressure  at  A.  Had  the  theoretical  line  F  been  run  to  the  boiler  pressure 


TWENTY  YEARS  WITH  THE  INDICATOR. 


209 


line  D,  it  would  have  shown  that  the  use  of  about  one-third  the  amount  of 
steam,  properly  cut  off,  would  have  performed  much  more  work,  if  it  had 
not  been  for  other  defects,  of  which  we  shall  shortly  speak.  The  diagram, 
in  this  case,  shows  on  its  cut-off  and  expansion  line,  an  exceedingly  close 

approximation  to  the  side  of  an 
old-fashioned  iron  wedge.  It  is 
extremely  difficult  to  locate  the 
point  of  cut-off,  or  to  find  out 
where  the  expansion  line  begins, 
and  the  approximation  to  any- 
thing which  is  valuable  or  eco- 
nomic is  so  entirely  remote  that 
we  will  not  waste  further  time 
upon  that  portion  of  the  diagram. 
The  theoretical  line  F  shows  a 
close  approximation  of  the  termi- 
nal pressure  as  between  the  theo- 
retical and  actual,  demonstrating 
that  an  amount  of  steam  bounded 
by  the  line  B,  cut  off  on  C,  was 
about  equivalent  to  the  amount  of 
steam  used,  taking  the  assumed 
line  F  with  the  actual  line  of  the 
instrument. 

In  this  case,  we  find  the  ex- 
treme terminal  about  in  unison 
with  the  theoretical,  but  back  of 
that  where  we  suppose  the  ex- 
haust valve  commences  to  open 
(for  the  lines  are  indistinct  and 
indefinite)  it  is  several  points 
higher.  But  the  main  feature  now 
is,  the  trouble  in  getting  rid  of  the 
exhaust  steam,  one  line  is  dotted 
and  the  other  is  solid ;  they  have 
both  a  peculiar  hump,  showing 
either  that  the  exhaust  passage  is 
clogged  by  insufficient  ports,  or 
FIG.  137.  what  is  more  apt  to  be  the  case, 

and  what  we  at  once  decided  when 

submitted  to  us,  that  the  steam  from  one  end  of  the  valve  passed  into  the  ex- 
haust about  the  center  of  the  stroke,  for  a  brief  space  of  time,  increasing  the 
back  pressure.  A  variety  of  theories  were  advanced,  one  of  which  was  that  the 
valves  were  not  tight,  but  would  in  time  wear  down  to  a  seat.  Whenever  an 
engineer  finds  this  kind  of  a  diagram,  the  shortest  way  out  is  to  abandon  the 
whole  thing,  or  condemn  the  engine  and  get  it  into  the  scrap-pile  as  soon  as 


2  10 


TWENTY  YJKAfiti  WITH  THE  INDICATOR. 


possible.  It  is  so  exceedingly  extravagant  in  its  use  of  steani  for  the  small 
amount  of  power,  and  considering  the  fact  that  it  was  intended  as  an  auto- 
matic cut-off  engine,  that  it  is  unworthy  further  attention,  its  only  purpose  of 
introduction  being  that  it  is  an  incident  in  practice  which  may  be  valuable  to 
some  one  in  trouble. 

As  the  best  way  to  judge  between  bad  and  good  practice  is  by  com- 
parison, we  introduce  into  this  lesson  another  diagram,  which  was  not  taken 
by  the  Thompson  indicator,  partially  to  show  the  expansion  line,  about  which 
more  or  less  argument  has  been  made  among  indicator  makers  for  the  last  few 
years,  and  also  to  contrast  it,  with  the  circumstances  all  stated,  with  Figs.  136 
and  137  in  this  lesson,  and  the  four  succeeding  figures  in  the  next  lesson  fol- 
lowing. 

Diagram  Fig.  138  is  an  exact  reproduction,  taken  from  one  of  George  H. 
Corliss'  steam- jacketed  new  pattern  engines,  boiler  pressure  75,  30  inches 


D 


,-! 


FIG.  138. 

diameter  of  piston,  72  inches  stroke,  54  revolutions,  40  scale.  This  engine  is 
driving  a  flour  mill  in  the  City  of  New  York,  has  been  running  fy  years,  about 
140  hours  per  week,  and  from  six  o'clock  Monday  morning  until  six  o'clock  or 
midnight  Saturday  night,  the  throttle  valve  is  never  closed.  The  engine  is 
grinding  about  1400  barrels  of  flour  every  24  hours  and  its  weekly  run 
amounts  to  143  hours  each  week.  The  indicated  horse-power  is  about  575 
H.  P.  We  have  66  pounds  initial  pressure  out  of  a  boiler  pressure  of  75  ; 
the  line  A  is  the  base  line  of  the  demonstration  which  gives  B  D  as  the  point 
of  cut-off  on  D,  or  the  volume  of  the  cylinder  represented  by  the  dotted  line 
C  D  in  proportion  to  the  whole  length  of  stroke,  as  that  portion  of  the  cylin- 
der which  was  filled  with  steam  at  initial  pressure  to  accomplish  the  work. 
Making  the  demonstration  from  A  B,  by  means  already  described,  we  have  the 
points  a,  a,  a,  etc.,  showing  the  exact  line  of  the  theoretical  in  comparison 
with  the  actual.  The  line  D  is  drawn  triflingly  above  the  actual  line  of  the 
(nstrument,  or  nearly  two  pounds  above,  in  order  to  show  the  actual  record  of 
the  indicator ;  for  that  reason,  a  slight  difference  is  made  in  the  position  of 


TWENTY  YEARS  WITH  THE  INDICATOR.  211 

the  lines,  showing  the  points  through  which  the  theoretical  curve  runs,  but 
whatever  that  difference  may  be,  it  is  so  near  to  the  width  of  a  line  as  to  be  a 
feature  of  no  possible  account  in  variation,  and  would  be  hardly  recognizable 
had  the  line  D  been  drawn  directly  through  the  steam  line  of  the  diagram. 

There  is  no  mistake  about  the  work  which  this  engine  is  doing,  provided 
the  indicator  is  correct,  and  it  is  hardly  probable  that  any  great,  difference 
exists  with  the  action  of  the  indicator ;  but  there  is  a  point  in  connection  with 
this  expansion  line  which  is  treated  of  in  the  next  lesson,  to  which  our  readers 
will  do  well  to  pay  careful  attention,  and  that  is  in  relation  to  the  change  of 
pressure,  volume,  temperature,  etc.,  and  whether  the  expansion  line  in  this 
diagram  is  an  absolute  reproduction  of  fact ;  this  will  be  illustrated  in  the  im- 
mediately succeeding  lesson. 

With  regard  to  adjustment  of  this  engine,  little  can  be  said  other  than  if 
we  were  ourselves  adjusting  the  valves,  we  should  give  it  a  slightly  earlier  re- 
lease, so  as  to  let  the  exhaust  line  down  where  it  belongs,  and  this  in  turn 
would  give  us  the  fine  dotted  line  for  compression,  which  we  should  much 
prefer  to  see.  This  diagram  was  not  taken  with  any  preparation,  change  or 
otherwise,  but  was  taken  while  the  engine  was  at  its  regular  work,  and  speaks 
not  only  for  its  builder,  but  as  well  for  the  care  which  has  been  given  it  by 
the  chief  engineer.  This  shows  an  exceedingly  close  approximation  as  be- 
tween practical  and  theoretical,  where  everything  is  in  working  order,  well 
taken  care  of,  doing  severe  work  and  running  foi  practically  twenty-four 
hours  per  day,  six  days  each  week.  No  new  valves  and  no  lost  time  are  yet 
charged  to  this  engine. 


LESSON  LXXI. 


AN  EXPERIMENT  WITH  INDICATORS  ON  THE    SAME  END  OF  THE  SAME 

CYLINDER,  AT  THE  SAME  TIME,  WITH  THE  SAME 

SPRINGS  IN  EACH. 

Fig.  139  was  taken  from  a  9^x12  Armington  &  Sims  engine,  runningr 
276  revolutions  per  minute,  80  pounds  of  steam,  40  spring.  The  pattern  of 
indicator  with  which  this  was  taken,  is  what  is  now  known  as  the  old  Thomp- 
son, with  what  was  practically  the  Richards  parallel  motion,  or  a  very  much 
heavier  motion  than  that  which  is  used  on  the  Improved  Thompson  of  to-day. 
Some  of  the  indicator  makers  have  put  out  some  very  curious  literature  in 
the  way  of  circulars,  showing  the  defects  of  each  other's  indicator,  according 


212 


TWENTY  YEARS  WITH  THE  INDICATOR. 


to  the  figures  which  accompany  the  circulars  or  pamphlets  which  have  been 
spread  broadcast.  The  experiment  which  we  are  to  record  here,  was  made  for 
the  purpose  of  ascertaining  what  the  indicators  will  do,  in  actual  practice ; 
and  we  desire  at  this  point  to  call  the  attention  of  our  readers  to  what  we 
have  very  radically  differed  from  many  of  the  engineers,  with  reference  to 
the  expansion  line  of  the  instrument,  and  the  record  which  is  made  by  the 
action  of  the  indicator  on  particular  points,  and  we  are  glad,  therefore,  to 
show  Fig.  139.  At  A  we  have  a  realized  pressure  of  76  pounds,  at  B  35 
pounds,  at  C  16  pounds,  at  D  9  pounds,  and  at  E  the  expansion  line  crosses 
the  atmospheric  line,  and  when  the  exhaust  valve  opens  at  the  termination 
of  the  stroke,  the  pressure  rises  gradually  until  about  one  pound  above,  when 
it  returns  across  the  expansion  line  at  E,  passing  along,  gradually  increas- 
ing to  F  as  the  valve  is  closing,  until  at  F  it  is  closed,  when  the  pressure 
rises  rapidly.  This  diagram  is  one  of  many,  and  is  taken  without  any  par- 
ticular selection. 


FIG.  139. 

We  will  now  refer  to  Fig.  140,  which  was  taken  by  another  indicator, 
with  the  same  spring  as  stated  above.  The  two  diagrams,  139  and  140,  were 
taken  on  the  same  stroke  of  the  engine,  with  the  same  steam  pressure,  each 
indicator  run  by  a  separate  cord,  and  a  slight  difference  in  the  length  of  the 
cards  is  shown.  The  peculiarity  of  the  two  cards  is  perfectly  perceptible  to 
any  one.  In  Fig.  140,  we  start  off  at  A  with  a  pressure  of  65  pounds  initial. 
At  B  we  have  51  plus,  at  C  48,  at  E  27,  at  F  15,  at  G  8.  A,  however,  is  the 
height  of  the  compression  line  which  falls  off  to  D,  rebounds  to  B,  comes 
down  to  C,  during  the  time  that  the  valve  is  opening,  and  then  starts  off  to 
the  left,  making  the  first  curve  in  the  steam  line.  The  rebound  of  pressure, 
by  the  sudden  expansion,  increase  of  volume,  and  the  struggle  between  the 
elements  and  the  speed  carry  the  expansion  line  below  the  compression  line 
on  the  card,  and  when  the  next  fluctuation  in  pressure  occurs,  at  E,  in  the 
forward  movement  of  the  engine,  and  the  rapid  expansion  and  falling  of 
pressure,  the  expansion  line  crosses  the  compression  line,  making  the  second 
wave  at  D  ;  dropping  to  F,  it  covers,  but  does  not  cross,  and  then  advances 


TWENTY  YEARS  WITH  THE  INDICATOR. 


213 


again,  the  oscillations  becoming  less  and  less  perceptible,  until  they  barely 
cross  the  atmospheric  line  at  the  end  of  expansion,  and  come  back  upon  the 
atmospheric  line  alone  until  the  compression  line  is  made.  There  is  such  a 
radical  difference  as  between  the  two  diagrams  that  one  must  be  nearer  right 
than  the  other,  and  one  must  be  exceedingly  far  from  correct.  We  have 
settled  in  our  own  mind  that  139  shows  the  position  of  the  valves,  and  the 
action  of  the  steam. 

Bat  there  are  other  elements  to  be  brought  into  this  lesson.  It  has  been 
upon  one  part  of  the  indicator-using  fraternity,  their  earnest  endeavor  to  rec- 
oncile all  differences  of  position,  all  fluctuations  of  working,  to  the  idea  of 
making  a  smooth  card,  for  which  see  140, 142.  We  have  frequently  had  cause 
to  say  editorially,  and  before  different  audiences,  that  we  had  been  unable  to 
reconcile  all  these  differences  which  do  take  place  in  the  steam  cylinder  of  an 
engine,  to  the  theory  that  a  steam  engine  indicator  must  of  necessity  produce 


FIG.  140. 

the  true  hyperbolic  curve,  or  the  nearest  approximation  to  it,  with  a  correctly 
working  indicator.  Inferentially  we  have  condemned  this  as  all  wrong,  and 
believe  that  the  various  elements  entering  into  the  expansion  line  of  high 
speed  diagrams,  if  correctly  delineated  by  the  indicator,  will  very  much  more 
approximate  139  and  141  than  they  will  140  and  142,  both  as  to  the  position 
of  the  valves,  and  actual  record  of  the  working  of  the  steam  in  the  cylinder. 
If  we  take  139,  we  find  from  A  to  B  a  change  of  41  pounds  pressure,  in  140  we 
find  from  C  to  E  a  change  of  21  pounds  pressure.  If  we  take  the  tempera- 
ture of  the  steam  at  A  on  139,  we  find  it  308.4°,  at  B  it  is  259.3°,  while  at  C 
it  is  only  216.3°.  Let  us  now  see  what  the  volume  in  each  case  is.  At  A  the 
volume  is  377,  at  B  764,  at  C  1572.  If  this  were  the  only  element  it  would 
be  quite  enough  to  produce  the  radical  changes  shown  in  139.  If,  now,  we 
refer  to  the  dotted  lines,  showing  the  friction  load,  in  Fig.  142,  we  find  there 
a  diagram  taken  with  a  stiffer  spring,  which  almost  absolutely  ignores  any 
fluctuations  in  temperature,  pressure  or  volume.  Referring  to  the  solid  line 
in  141,  which  represents  the  friction  card,  with  the  Thompson  indicator,  with 


2i4  TWENTY  YEARS  WITH  THE  INDICATOR. 

the  same  spring  as  142,  we  find  these  differences  very  elegantly  shown  in  the 
load,  and  plainly  perceptible  in  the  friction  card,  which  is  enclosed  within  the 
other.  Both  these  diagrams  in  141  and  142  were  taken  by  preparing  for  it 
beforehand,  so  as  to  throw  a  break  upon  a  pulley,  properly  connected,  raising 
the  load  from  the  friction  to  the  amount  shown,  in  the  shortest  space  of  time 
consistent  with  safety  to  those  employed.  Now,  if  nothing  except  the  volume 
and  the  temperature  were  to  be  considered,  we  have  then  elements  of  immense 
disturbance,  as  shown  by  the  figures  quoted.  In  Fig.  139  the  volume  in- 
creases in  the  fraction  of  a  second  from  377  to  20,890  at  E  ;  while  in  Fig.  140 
the  volume  increases  from  434  to  20,890,  and  the  temperature  diminishes  in 
the  fraction  of  a  second  from  308.4°  to  102°.  But  if  we  refer  to  Mr.  Charles 
T.  Porter's  book,  entitled  the  "  Bichards  Steam  Engine  Indicator,"  which  has 
been  in  oar  possession  for  fifteen  years  at  this  writing,  we  find  the  most  re- 
liable  and  best  tabulated  data  that  we  have  ever  yet  had  access  to,  with  ref- 
erence to  the  speed  of  the  crank  at  different  degrees  in  the  steam  engine,  as 
well  as  to  the  speed  of  the  crank  as  compared  with  that  of  the  piston.  We 


FIG.  141. 

find  the  following   statement  with  reference  to   the  rotative  force  exerted 
upon  the  crank,  being  the  same  for  equal  divisions  of  the  diagram : 

"  If  the  reciprocating  parts  of  engines  were  without  weight,  so  that  the 
pressure  of  the  steam  was  always  exerted  upon  the  crank  precisely  as  it  is  on 
the  piston,  then  the  rotative  force  on  the  crank  of  the  steam  pressure  would 
be  equal  for  equal  divisions  of  the  diagram  measured  at  any  part  of  the 
stroke.  This  is  often  denied,  and  still  more  often  doubted.  Being  a  fact,  it 
ought  to  be  placed  beyond  either  denial  or  doubt.  The  motion  of  the  crank 
is  supposed  to  be  uniform,  passing  through  equal  arcs  in  equal  times,  the 
motion  of  the  piston,  on  the  contrary,  is,  first,  scarcely  two-thirds  that  of  the 
crank,  being  to  the  latter  in  proportion  of  1:1.5708,  and,  second,  it  changes 
at  every  point  of  the  stroke.  At  the  instant  that  the  crank  is  on  the  dead 
center  the  piston  has  no  motion.  Then  its  motion,  at  first  infinitely  slow, 
becomes  gradually  accelerated,  until  the  velocities  of  the  piston  and  the  crank 
are  equal,  when  it  begins  to  be  retarded,  the  ratio  of  retardation  increasing 
until  on  the  opposite  center  its  motion  has  ceased.  But  whether  the  revolu- 
tion of  the  crank  is  uniform  or  not, — as  in  fact  it  can  never  be  absolutely, 
since  then  the  fly-wheel  would  cease  to  act  as  a  regulator,  and  might  be  dis- 
pensed with, — the  motion  of  the  piston  has  a  fixed  relation  to  it,  being  equal 


TWENTY  YEARS  WITH  THE  INDICATOR.  215 

(if  we  disregard  for  the  present  the  effect  of  the  angular  vibration  of  the  con- 
necting rod)  to  the  versed  sine  of  the  angle  which  the  crank  makes  with  the 
center  line.  The  study  of  the  table  of  versed  sines  will  explain  all  about  it. 
We  will  employ  the  two  extremes  for  illustration.  The  versed  sine  of  1°  is 
.0001523;  the  difference  between  the  versed  sine  89°  and  that  of  90°  is 
.0174524.  Therefore,  the  length  of  the  crank,  or  of  the  half  stroke  of  the 
piston,  being  1,  while  the  crank  is  traversing  the  first  degree  the  piston 
moves  the  distance  .0001523,  and  while  the  crank  is  traversing  the  ninetieth 
degree  the  piston  moves  the  distance  .0174524,  which  is  nearly  115  times 
greater  than  the  former.  The  rotative  effect  of  a  force  varies  also  as  the 
versed  sine  of  the  angle  at  which  it  is  applied.  Therefore,  the  effect  of  the 
rotative  pressure  of  the  steam  on  the  crank  while  it  is  traversing  the  ninetieth 
degree  is  115  times  as  great  as  while  it  is  traversing  the  first  degree,  but 
also  the  piston  moves  in  the  former  case  115  times  as  far  as  in  the  latter.  It 
follows,  therefore,  that  equal  movements  of  the  piston,  or  equal  portions  in 
the  length  of  the  diagram,  at  any  part  of  the  stroke,  represent  equal  rotative 
effects  upon  the  crank." 


FIG.  142. 

"We  have  made  this  lengthy  quotation,  first,  because  Mr.  Porter  has  so 
well  said,  and  has  substantiated  his  assertion  by  indisputable  fact,  and,  sec- 
ond, while  we  are  not  dealing  in  this  lesson  with  the  rotative  force  on  the 
crank  we  are  dealing  with  the  speed  of  the  piston,  and  will  now  drop  our 
digression  and  return  to  the  subject  in  hand.  Added  to  the  extreme  range  in 
temperature,  as  well  as  the  tremendous  increase  in  volume,  we  have  now 
another  factor  which  shows  us  that  the  difference  between  the  travel  of  the 
piston  through  the  first  degree  of  the  stroke  and  the  last  degree  of  the  stroke 
is  115  times  ;  we  have  then  precisely  what  we  require  to  substantiate  our 
own  assertion,  that  if  the  indicator  is  to  be  the  exponent,  or  is  to  truly  record 
what  is  actually  done  in  the  cylinder,  then  it  must  also  record  these  extreme 
ranges  of  fluctuation  in  pressure,  volume,  temperature,  all  of  which  are  gov- 
erned by  the  varying  speed  of  the  piston.  We  have,  therefore,  just  these  ele- 
ments ;  referring  to  diagrams  139  and  141,  from  A  to  D,  in  139,  the  speed  of 
the  piston  is  constantly  increasing,  the  pressure  of  the  steam,  as  shown  by 
the  indicator  diagram,  falls  very  rapidly,  the  temperature  decreases  very  fast 
indeed,  while  the  volume  increases  at  a  tremendous  rate ;  the  speed  of  the 
engine,  being  276  revolutions,  reduces  the  time  in  which  this  diagram  is  made 
to  about  one-tenth  of  one  second,  or  that  portion  of  it  which  lies  between  C 


2i6  TWENTY  YEARS  WITH  THE  INDICATOR. 

and  D  is  reduced  to  fa  of  a  second  12100  of  a  minute  approximately,  more  cor- 
rectly being  y-jVr »  a^d  when  we  add  to  this  the  fact  that  the  speed  of  the  pis- 
ton is  an  ever- varying  amount — anything  but  constant — we  do  not  hesitate  to 
state  that  while  our  assertion  may  have  been  doubted  or  denied,  it  is  sus- 
ceptible of  proof,  and  that  proof  we  believe  is  offered  in  these  elements  be- 
yond dispute,  if  the  facts  are  considered. 

Figs.  141  and  142  were  taken  with  a  60  spring  to  ascertain  what  differ- 
ence, if  any,  would  be  shown  as  between  two  instruments  on  the  same  engine, 
at  the  same  speed,  with  the  same  steam  and  spring,  and  at  the  same  instant 
of  time  ;  141  was  taken  with  the  Thompson  instrument,  with  the  new  or  Im- 
proved Thompson,  with  the  light  parallel  motion.  In  141,  we  have  dotted 
the  outside  or  total  load  and  drawn  the  friction  of  the  engine,  so  far  as  we 
could  do,  in  a  solid  line.  In  Fig.  142,  we  have  been  obliged  to  reverse  this 
operation,  owing  to  the  fact  that  the  friction  crosses  the  initial.  The  two 
diagrams  may  be  treated  from  any  standpoint,  and  only  require  a  careful 
observation  to  convince  any  person,  who  is  disinterested,  where  the  actual 
position  of  the  valves  and  the  working  of  the  steam  is  shown.  To  our 
own  idea  141  shows  every  element  of  accuracy,  while  142  shows  quite  a 
different  result  for  power  and  position  of  the  valves  ;  and  we  may  in  this 
connection,  perhaps,  with  perfect  propriety,  quote  again  from  Mr.  Porter's 
book,  as  follows : 

''VIBRATIONS  OF  THE  SPRING. 

"  Sometimes  at  very  high  speeds,  or  with  very  sudden  action  of  the  steam, 
the  spring  of  the  indicator  is  put  into  vibration.  If  the  line  produced  by 
these  vibrations  is  a  waving  line,  quite  free  from  angles,  this  is  an  evidence 
that  the  action  of  the  instrument  is  frictionless,  and  the  mean  of  the  vibra- 
tion gives  a  true  line."  Almost  on  the  same  page  Mr.  Porter  makes  this  state- 
ment :  "  There  are  no  vibrations  or  pulsations  of  steam  in  the  cylinder  ;  all 
appearances  of  this  kind,  on  the  expansion  curve,  are  caused  by  the  spring  of 
the  indicator  being  put  into  vibration  by  the  sudden  action  of  the  steam." 

If  the  vibrations  do  not  occur  while  the  engine  is  under  motion,  or  if  the 
pulsations  are  not  caused  by  the  conflict  in  the  molecules  of  steam,  or  steam 
and  water,  as  well  as  the  different  mechanical  forces,  then  we  confess  that  our 
steam  engine  indicator  had  better  be  laid  upon  the  shelf  instantly,  there  to 
remain  until  we  can  prove  that  different  mechanical  forces,  acting  as  we  have 
cited  above,  are  capable  of  producing  a  true  hyperbola  by  means  of  a  spiral 
spring.  Whatever  may  be  the  fact  with  regard  to  pulsations,  we  call  par- 
ticular attention  to  the  difference  in  the  outline  which  shows  the  position  of 
the  valve,  as  between  141  and  142,  while  the  differences  between  139  and  140 
are  quite  sufficient  for  anyone,  however  unsophisticated  he  may  be  in  the 
uses  or  abuses  of  the  indicator.  In  our  own  experience  in  taking  diagrams 
with  different  indicators  upon  the  same  end  of  the  engine,  at  the  same  speed, 
and  under  the  same  conditions,  we  have  found  that  diagrams  showing  wavy 
lines,  figure  somewhat  less  power,  and  give  generally  a  more  accurate  idea  of 
the  working  of  steam  in  the  cylinder,  and  that  the  same  indicator  also  sooner 


TWENTY  YEARS  WITH  THE  INDICATOR.  217 

responds  to  any  actual  alteration  made  in  the  valve  motion,  by  showing  it 
upon  the  diagram,  showing  that  its  accuracy  extends  into  this  important 
realm  of  the  functions  of  the  indicator,  viz. :  position  of  valves,  while  the  stiff- 
working  indicators  do  not  show  it  as  soon  nor  as  delicately. 


LESSON  LXXII. 


EXTREME   HIGH   SPEED,   DIFFERENCE  IN  INDICATORS. 

The  tendency  to  high  speed  has  led  to  some  very  curious  developments, 
and  one  of  the  principal  claims  of  engine  builders,  as  well  as  indicator 
makers,  to-day,  is,  that  their  engine,  or  their  indicator,  is  the  most,  if  not 
the  only,  reliable  one  at  high  speed.  High  speed,  it  has  been  proved  to  our 


THOMPSON,  No.  2.  FIG.  143. 

own  satisfaction,  has  a  limit  where  efficiency  ends  and  extravagance  begins, 
and  while  we  have  no  purpose  in  this  article  to  criticise,  we  must  express  ou.1 
opinion  so  that  we  may  not  be  placed  on  record  as  advocating  the  speed  (at 
which  the  diagrams  illustrated  in  this  lesson  were  taken)  for  practical 
purposes. 

These  diagrams  were  taken  in  the  shop  of  Armington  &  Sims,  Provi- 
dence, K.  I.,  where  they  had  prepared  an  engine  by  increasing  the  strength 
of  some  of  the  parts  of  the  regulator,  and  our  intention  was  to  have  carried 
the  experiment  to  700  or  more  revolutions  per  minute.  Diagram  143  was 
taken  with  a  Thompson  Improved  Indicator,  No.  2,  on  small  paper  barrel,  an 
illustration  of  which  is  given  with  this,  which  differs  from  the  larger  indi- 
cator only  in  the  size  of  paper  barrel,  and  some  minor  changes  with  reference 
to  the  stand,  the  spring  and  motion  being  the  same  as  that  in  the  larger 


218 


TWENTY  YJEAES  WITH  THE  INDICATOR. 


instrument.  This  instrument  is  made  with  or  without  the  detent  motion, 
generally  with  the  detent  motion  ;  this  is  a  matter  which  is  invaluable  to 
those  who  are  unused  to  high  speeds,  or  are  not  familiar  with  the  practice  of 


FIG.  144. 

taking  indicator  diagrams,  and  it  is  especially  valuable  to  those  who  are 
taking  diagrams  from  the  locomotive.  Fig.  143  was  taken  with  this  instru- 
ment in  April,  1884,  at  a  speed  of  536  revolutions  per  minute,  actual  count, 
the  regulator  being  graduated  and  adjusted  for  that  point.  The  reader  will 
necessarily  have  to  compare  several  diagrams,  one  with  another ;  for  this 
purpose,  with  the  exception  of  Fig.  149,  we  have  in  this  article,  dotted  the 
steam  line  and  drawn  the  expansion  line  solid  in  all  the  figures. 


FIG.  148. 

In  Fig.  143,  it  will  be  seen  that  the  expansion  crosses  the  atmospheric 
in  the  vibrations,  and  returns  again,  making  a  very  handsome  atmospheric 
line,  and  that  the  compression  line  crosses  the  first  or  largest  vibration,  but 
that  the  steam  line  is  very  handsomely  shown.  Fig.  144  was  taken  by  an 
instrument  from  another  maker ;  it  will  be  seen  in  this  case  that  there  is  a 
very  great  difference  between  the  atmospheric  line  and  compression  line. 


TWENTY  YEARS  WITH  THE  INDICATOR, 


219 


Fig.  143  was  taken  with  a  50  spring,  144  with,  a  40  spring.  Fig.  145  was 
taken  with  the  same  instrument  as  144,  at  a  speed  of  536  revolutions  ;  there 
being  such  a  difference  between  143  and  144  as  to  position,  that  146  was 


FIG.  146. 

taken  with  the  little  Thompson,  the  spring  being  changed  tc  40,  the  speed 
being  increased  to  562.  It  will  be  noticed  here  that  a  change  takes  place  in 
the  admission  and  steam  line,  which  continues  through  the  other  diagrams, 
the  motion  of  the  valve  being  shown  as  a  trifle  late,  the  expansion  line  hav- 
ing its  peculiarities,  but  the  record  being  very  clear.  The  steam  pressure  in 
146  was  75  pounds.  To  ascertain  what  could  be  done,  we  again  changed  the 
spring  to  50,  the  steam  meantime  having  been  raised  to  95  pounds,  and  ob- 
tained from  this  change  Fig.  147,  with  the  Thompson  No.  2,  revolutions  562, 


FIG.  147. 

For  the  sake  of  experiment,  arrangements  were  then  made  to  add  a  load 
to  the  engine,  and  Fig.  148  was  taken  with  the  Thompson  Improved  No.  2, 
steam  pressure  92  pounds.  The  peculiarities  in  146,  147  continue  with 
reference  to  the  valve  motion,  showing  it  a  trifle  late  ;  the  compression  and 
expansion  lines  are  very  nearly  identical,  except  that  the  load  is  increased. 
Upon  148  we  have  erected  the  demonstration  from  exactly  half  stroke,  the 
line  A  being  the  base  line,  showing  the  cut-off  to  be  at  B,  on  C,  and  for  the 


220 


TWENTY  YEARS  WITH  THE  INDICATOR, 


terrific  speed  at  which  it  is  running,  there  is  a  very  good  showing  for  the 
valves  as  well  as  the  indicator.  Having  so  far  determined  that  the  action  of 
the  indicator  was  at  least  capable  of  showing  changes,  an  effort  was  made  to 


FIG.  145. 

increase  the  speed  of  the  engine  from  562  to  700,  the  regulator  was  changed 
as  much  as  it  was  deemed  safe  and  a  start  was  made,  producing  Fig.  149 
with  the  new  Thompson  No.  2,  at  a  speed  of  642  revolutions  per  minute. 
Two  other  cards  were  produced,  and  while  changing  for  the  fourth  one,  a  piece 
of  the  regulator  which  had  been  made  of  steel,  straightened  out  by  the  strain 
upon  it,  and  we  were  treated  to  an  example  of  solid  bodies  going  off  at  a 


FIG.  149. 

tangent,  and  the  engine  was  stopped  for  repairs.  The  ordinary  speed  of 
this  engine  is  320  or  330  revolutions  ;  the  action  of  the  regulator  shows 
plainly  on  149,  with  95  pounds  boiler  pressure,  and  an  initial  of  90:92,  the 
load  was  made  constant,  but  it  is  absolutely  impossible  to  engrave  the 
variations  which  took  place,  only  at  the  curves  in  the  expansion  line.  The 
intention  at  the  outset  of  this  experiment  was  to  try  the  three  indicators 
which  are  in  the  market ;  one  of  them  stopped  inside  of  400,  one  ceased  its 


TWENTY  YEARS  WITH  THE  INDICATOR.  221 

accuracy  practically  at  536,  or  probably  below,  while  tlie  third  one  made  the 
diagrams  which  we  have  shown,  leaving  the  little  Thompson  master  of  the 
situation  in  this  experiment. 

We  have,  since  that  time,  been  allowed  to  test  an  engine  more  for  speed 
than  anything  else,  and  have  succeeded  in  getting  very  fair  diagrams  at  above 
720,  but  the  action  of  the  steam  shows  plainly  that  the  engine  will  not 
become  a  merchantable  or  commercial  affair,  and  there  is  no  use  in  devoting 
space  to  that  which  is  not  practical ;  we  do  not  consider  this  lesson  as  one 
of  any  particular  importance  for  the  student  of  the  indicator,  and  it  is  intro- 
duced more  as  a  curiosity  to  show  the  results  of  a  single  experiment,  upon 
which  we  do  not  place  any  particular  stress,  and  would  not  advise  any  person 
to  buy  the  Thompson  indicator  solely  upon  what  is  shown  in  this  lesson,  or 
not  to  buy  either  one  of  the  other  two  because  of  their  ill  success  at  this 
experiment.  One  of  the  makers  of  the  engine  was  present  and  saw  all  the 
experiment.  The  intention  was  fully  pursued  of  giving  to  each  instrument 
every  benefit  and  every  advantage,  and  the  results  shown  are,  as  nearly  as 
possible,  the  actual  result  of  the  work  of  the  instruments.  We  do  not,  how- 
ever, advise  our  readers  to  adopt  any  such  speed,  nor  do  we  consider  the 
actual  indicator  diagram  at  this  speed  as  an  unquestioned  performance.  The 
claim  has  been  made  that  diagrams  have  been  taken  at  above  1000  ;  while  we 
have  no  reason  to  doubt  the  assertions,  we  consider  them  simply  experi- 
mental, or  in  the  light  of  a  curiosity,  and  having  no  possibility  of  practical 
value,  unless  it  be  to  gratify  a  whim,  which  cannot  result  in  any  economy 
to  the  general  steam  user,  at  least  with  present  engines,  indicators  or 
mechanism. 


LESSON  LXXIII. 


AMERICAN  BUILT  COMPOUND  STEAM  ENGINE  FOR  A  RIVER  STEAMER, 

The  question  of  simple  condensing  engines,  or  of  compound  engines,  for 
our  river  steamers  has  been  one  upon  which  a  great  diversity  of  opinion  has 
been  expressed,  and  in  which  the  extremes  of  practice  have  been  worked  out 
within  the  last  few  years.  Wishing  to  get  data  regarding  this,  we  asked  and 
obtained  permission  to  indicate  a  river  steamer's  compound  engine  working  a 
screw,  and  this  steamer  is  doing  the  work  with  about  one-half  the  fuel  that  a 
condensing  beam  engine  did  it,  and  is  one  of  the  fastest  steamers  for  her 
class  running  out  of  New  York. 


222 


TWENTY  YEARS  WITH  THE  INDICATOR. 


Fig.  150  is  the  high-pressure  diagram,  taken  with  a  50  spring,  the  cylin- 
der being  30  inches  in  diameter,  36  inches  stroke,  making  88  revolutions  per 
minute,  with  85  pounds  of  steam. 

Fig.  151  is  from  the  low-pressure  cylinder  of  the  same  engine;  56  inches 
in  diameter,  36  inches  stroke,  making  88  revolutions,  scale  of  spring  10.  The 
diagrams  were  taken  at  the  same  instant  of  time,  two  indicators  being  used, 
so  that  they  represent  what  was  done  on  the  same  stroke  at  the  same  instant 
of  time. 

In  Fig.  150,  A  is  the  base  line  of  the  demonstration,  which  touches 
through  the  theoretical  curve  Gr,  the  realized  steam  pressure  line  F,  at  B.  B 
represents  the  volume  of  steam  actually  used  to  do  the  amount  of  work  at 
the  realized  pressure,  which  is  9  pounds  less  than  the  boiler  pressure  E.  The 
valve  in  opening,  as  will  be  seen,  allows  the  pressure  to  drop  slowly  from  the 
line  F  after  the  piston  has  passed  but  a  few  laches  of  its  stroke,  so  that  at 
the  point  B,  on  F,  the  realized  pressure  by  the  indicator  is  10  pounds  less 


FIG.  150. 

than  the  realized  pressure  at  the  commencement  of  the  stroke.  We  then  find, 
after  having  passed  pretty  well  toward  the  end  of  the  expansion  line,  that  the 
expansion  rises  above  the  theoretical  to  a  certain  extent.  The  exhaust  valve 
is  somewhat  slow  in  its  opening,  and  the  pressure  in  the  receiver  at  the  very 
highest  amounts  to  between  11  and  12  pounds.  The  same  general  features 
will  apply  to  the  valves,  both  high  and  low-pressure  cylinders,  viz.,  that  the 
opening  of  the  valve  seems  to  be  either  slow  or  insufficient,  and  the  pressure 
gradually  drops  from  and  after  the  time  when  the  valve  opens,  and  owing  to 
this  feature  it  is  also  slow  in  closing,  and  the  amount  of  steam  accounted  for 
is  considerably  in  excess  of  that  which  is  generally  considered  shown  by  the 
indicator.  If  we  refer  to  151,  taken  with  a  10  scale,  we  charge  against  that 
cylinder  12  pounds  initial  pressure,  which  is  the  extreme  amount  shown  in 
the  high-pressure  cylinder  as  back-pressure  or  between  the  high-pressure  and 
low-pressure  cylinder.  The  lines  I  and  I'  represent  respectively  the  steam 
admission  from  the  receiver  to  the  low-pressure  cylinder.  If  we  refer  to  the 
line  I  we  see  that  after  the  steam  is  first  introduced  the  pressure  is  kept  at 


TWENTY  YEARS  WITH  THE  INDICATOR. 


223 


11  pounds  above  the  atmospheric  line  C  for  a  very  small  portion  of  the 
stroke ;  that  as  quick  as  the  speed  of  the  piston  begins  to  increase,  then  the 
pressure  of  the  steam  commences  to  drop  away,  until  at  the  line  B  there  is 
only  4  pounds  above  the  atmosphere,  and  at  the  point  of  visible  cut-off,  or 
where  the  valve  finally  closes,  there  is  only  two  pounds  above  the  atmos- 
phere. I',  while  not  making  so  good  a  start,  has  a  pressure  of  almost  three 
pounds  at  the  visible  point  of  cut-off,  which  is  considerably  beyond  the  line 
B'.  Now,  what  happens  ?  When  the  valves  of  this  engine  commence  to  open, 
the  steam  is  not  admitted  in  proper  amount,  owing  to  its  low  tension,  to  fill 
the  cylinder  at  the  pressure  which'  exists  in  the  receiver.  The  moment  the 
piston  starts  to  move  away  from  the  end  of  the  cylinder — and  the  motion  of  a 
piston  with  a  short  connecting  rod,  not  more  than  two  cranks,  accelerates 


B 


D 


B' 


FIG.  151. 

very  rapidly — then  the  amount  of  steam  which  is  admitted  grows  less  and  less 
or  is  more  and  more  wire-drawn.  The  steam  is  cut  off  at  the  line  B'  of  the 
other  diagram,  as  we  express  it,  visibly ;  or,  that  is,  the  point,  almost  two- 
thirds  of  the  stroke,  where  the  steam  valve  closes  and  the  expansion  on  the 
low-pressure  cylinder  begins.  If  we  go  a  step  further  to  the  line  A',  which 
is  the  base  of  our  computation,  we  find  at  that  point,  only  a  trifling  distance 
beyond  the  point  01  cut-off,  the  pressure  above  absolute  vacuum  is  about  14.3 
pounds.  Now,  had  we  here  cut  off  the  pressure  of  steam  at  B  to  make  the 
theoretical  line  G',  we  should  have  used  the  same  amount  of  steam,  practi- 
cally, and  have  expanded  down  the  line  G'  without  the  outlay  of  a  single 
pound  of  coal  more  than  we  are  now  using,  while  on  the  other  side  the 
dotted  theoretical  line  G  would  have  cut  off  at  B'  and  have  gone  down  the 
dotted  line,  utilizing  the  space  bounded  by  H,  I,  G  as  efficient  pressure  on 
the  piston,  instead  of  following  the  steam  lines  I  and  I'.  This  is  serious, 


224  TWENTY  YEARS  WITH  THE  INDICATOR. 

but  we  will  shortly  show  by  the  figures  what  would  be  produced  with  a  proper 
arrangement  of  the  valves.  The  line  D  is  the  vacuum  line  on  one  diagram, 
and  D'  the  vacuum  line  on  the  other.  It  will  be  noticed  there  is  a  peculiarity 
with  reference  to  the  vacuum  of  this  engine.  We  have  only  6.2  pounds  on 
one  end  and  7  pounds  on  the  other,  or  practically  12  J  inches  and  14  inches ; 
the  coarse  dotted  line,  F,  shows  what  we  should  have  realized  in  obtaining  a 
vacuum  of  12  pounds  or  24  inches.  These  diagrams  were  taken  on  the  night 
of  December  18, 1884,  when  the  water  was  certainly  cold  enough  to  have  pro- 
duced a  good  vacuum,  but  the  proportion  of  the  machinery  would  not  allow 
it.  Here,  then,  we  have  the  difference  between  D'  and  F,  which  should  have 
given  us  5  pounds  more  of  mean  pressure  effectually,  or  of  mean  effectual 
vacuum  more-  than  we  did  receive. 

These  are  the  general  features  and  facts  with  reference  to  the  diagram. 
The  engine  is  well  built,  well  proportioned,  seemingly,  and  the  boat  is  very 
fast  and  economical.  Now,  suppose  we  could  improve  it  in  design  or  in 
execution,  what  would  be  the  effect  ?  In  the  high-pressure  cylinder  we  have 
in  the  respective  ends  520.25  horse-power  on  the  bottom,  and  508.7  horse- 
power on  the  top ;  in  the  low-pressure  cylinder,  the  actual  diagram  by  the 
indicator  figures  389.24  horse-power  on  the  bottom,  and  332.55  horse-power 
on  the  top.  If  the  valves  had  worked,  so  that  we  could  have  obtained  our 
theoretical  diagram  by  opening  the  valves  sufficiently  to  feed  the  cylinder  with 
the  pressure,  cutting  it  off  sharply  so  as  to  make  the  theoretical  lines  or  close 
approximation  to  them,  and  only  have  obtained  the  same  vacuum  which  is 
shown  by  the  instrument,  we  would  then  have  attained  relatively  499.46 
horse-power  on  the  bottom  and  402.72  horse-power  on  the  top,  making  a  very 
radical  gain.  But  if  we  could  make  this  engine  still  more  perfect  in  its  work' 
ing,  so  as  to  admit  the  steam,  cut  it  off  and  then  produce  the  vacuum  of  12 
pounds,  we  should  have  had  a  very  different  result  indeed ;  it  would  then 
have  been  683.15  horse-power' on  the  bottom  and  616.29  horse-power  on  the 
top,  or  to  condense  it,  the  actual  diagrams  combined  show  now  852  horse- 
power on  the  top  and  897  horse-power  on  the  bottom.  With  proper  increase, 
it  would  give  1136  horse-power  on  the  top  and  1191  horse-power  on  the 
bottom,  or  would  make  a  still  further  difference  of  a  very  large  amount  in 
proportion  to  the  coal  which  the  steamer  burned,  if  these  results  were  real- 
ized. The  receiver  pressure  is  well  taken  care  of  by  the  low-pressure  cylin- 
der, but  the  whole  amount  of  steam  is  not  accounted  for  as  between  the  high 
and  low-pressure  above  the  atmospheric  line,  and  the  account  below  the 
atmospheric  line  on  the  low-pressure  cylinder  should  by  some  means  be  very 
radically  improved.  It  is  quite  possible  that  the  ports  and  passages,  and 
probably  the  throw  of  the  valves  in  this  engine,  are  all  based  upon  the  olden- 
time  practice  and  would,  upon  careful  investigation,  be  found  to  be  too  small 
in  area  or  too  short  in  valve  travel,  and  yet,  as  compared  with  previous  prac- 
tice, this  steamer  has  a  splendid  record.  The  only  question  now  is,  how 
much  higher  the  record  can  be  made  by  proper  adjustments  of  the  engine. 


TWENTY  YEARS  WITH  THE  INDICATOR.  225 


LESSON  LXXIV. 


A  COMPOUND  NON-CONDENSING  ENGINE. 

Very  frequently  diagrams  are  put  before  an  engineer  to  ask  his  general 
opinion,  and  while  there  is  no  information  of  a  positive  sort  to  be  gained 
from  this  lesson,  it  is  entirely  within  the  province  of  the  work  to  show  some 
things  with  which  working  engineers  are  frequently  annoyed  or  expected  to 
do  work  with  or  against  natural  obstacles,  in  their  way,  which  preclude 
economy,  regulation  of  speed,  or  any  other  practical  result.  Referring  to 
Fig.  152,  we  have  the  high-pressure  side  of  a  compound  non-condensing 
engine,  scale  30.  This  is  supposed  to  be  governed  by  a  throttle  governor  in 
the  pipe,  which  jumps  up  and  down  like  a  jack-in-the-box  ;  the  different  lines 
here  are  precisely  as  the  indicator  left  them.  It  will  be  seen  that  the  initial 


FIG.  152. 

pressure  of  steam  entering  the  cylinder  in  the  highest  instance  is  38  +  ;  it 
then  varies  to  27,  and  from  that  down  to  18.  Notice,  that  in  two  of  the  lines 
an  attempt  is  made  to  cut  off,  and  in  the  other  two  lines,  strange  as  it  may 
seem,  initial  pressure  is  below  the  maximum  pressure  by  several  pounds. 
The  back  pressure  amounts  to  between  three  and  four  pounds  at  the  com- 
mencement, and  runs  down  to  one  and  one-half  pounds  at  the  moment  of 
compression. 

Fig.  153  represents  the  low-pressure  side,  running  as  high-pressure  in 
connection  with  152.  This  arrangement  was  brought  about  by  shifting  a 
valve  between  the  cylinders,  so  as  to  allow  direct  steam  to  enter  into  both 
ends  and  sides.  The  scale  of  153  is  ten.  We  have  here  13  pounds  initial, 
but  with  an  exceedingly  great  variation  in  the  action  of  the  steam,  commenc- 
ing with  a  back  pressure  of  two  pounds,  running  up  to  four,  and  dropping 
back  to  three,  showing  that  there  is  some  peculiar  action  in  the  cylinder. 
Fig.  153  was  taken  after  154. 

Figs.  A,  B,  154  are  from  both  ends  of  the  compound  cylinder,  and  were 
taken  at  the  same  instant  as  152,  scale  ten.  We  have  an  initial  pressure  in 


226  TWENTY  YEARS  WITH  THE  INDICATOR. 

the  A  end  of  7  pounds,  which  falls  down  to  1J  pound  by  a  most  peculiar 
line.  It  then  runs  along  and  gradually  increases  to  2  pounds,  and  a  little 
later  to  3J.  Whether  this  obstruction  is  caused  by  the  peculiar  passing  of 
the  steam  through  the  double-ported  slide  valve  between  the  cylinders,  or 
whether  it  is  caused  by  the  motion  of  the  exhaust  valve,  we  have  not  deter- 
mined, not  being  enabled  to  examine  the  inside  or  working  parts  of  the  en- 
gine. The  expansion  in  either  case  is  most  peculiar,  and  the  terminal  of  this 
double  expansion  line  seems  to  be  slightly  below  the  atmospheric,  but  we 
have  the  same  general  formation  of  the  return  or  exhaust  line  which  passes 
above  the  line  of  direct  pressure  more  than  half  a  pound,  falling  back 
again  slightly  and  compressing  above  the  induction  pressure.  The  dia- 
gram, taken  altogether,  is  peculiar.  It  shows  but  an  exceedingly 
small  amount  of  power  exerted  upon  the  piston  as  the  back  pressure 
nearly  neutralizes  the  forward  pressure.  Turning  to  the  B  end  of  the  cyl- 
inder, we  have,  if  anything,  a  worse  diagram  than  the  A.  The  features,  it  will 
be  noticed,  are  very  similar  indeed  in  general,  but  there  is  a  little  difference 
of  outline.  The  extreme  amount  of  initial  pressure  is  only  about  five  pounds  ; 
that  barely  continues  for  an  inch  of  the  stroke,  when  what  we  suppose  to  be 


FIG.  153. 

the  expansion  line,  falls  away  similarly  to  that  of  the  A  end,  resting  on  the  at  • 
mospheric  line  for  an  instant  of  time  and  dodging  away  again  to  a  pressure  of 
nearly  three  pounds  at  the  maximum  on  the  second  introduction  of  steam.  In 
the  exhaust,  for  a  very  brief  interval,  the  line  returns  on  the  atmospheric 
pressure  line,  then  rises  very  materially  above  the  direct  steam  line  continu- 
ing two  pounds  above  the  atmospheric  line  with  only  five  pounds  of  initial 
pressure.  It  is  usually  supposed  in  compounding  that  some  gain  is  to  be 
derived.  In  this  case  there  is  no  economy,  and  what  the  gain  can  possibly  be 
by  compounding  a  high-pressure  engine  with  another  high-pressure  cylinder, 
one  side  doing  eight  and  one-half  times  as  much  power  as  the  other,  we  can- 
not imagine.  The  high-pressure  side  of  this  engine  is  doing  from  seven  to 
eight  and  one-half  times  the  amount  of  power  that  the  compound  is  doing. 
We  think  the  idea  of  high-pressure  compounding  is  entirely  a  mistake,  unless 
some  very  different  way  of  working  it  out  shall  be  adopted  from  that  shown 
in  this  lesson.  The  movement  of  the  governor  was  most  erratic,  and  we  have 
no  doubt,  if  the  different  parts  of  the  engine  were  compared  with  a  correctly 
moving  valve  motion,  that  all  the  ports  and  steam  passages  would  be  found 


TWENTY  YEARS  WITH  THE  INDICATOR.  227 

radically  differing  from  good  practice,  and  that  the  travel  of  the  valves  was 
very  ill-proportioned  to  the  travel  of  the  piston.  They  simply  take  their 
place  as  curiosities,  and  for  information  to  the  working  engineer,  which,  we 
hope,  very  few  of  them  will  ever  encounter,  especially  if  they  are  compelled 


FIG.  154. 

to  take  charge  of  them.  This  engine  is  burning  more  than  eight  pounds  of 
fuel  per  horse-power  per  hour,  if  the  data  given  of  the  amount  of  coal  burned 
is  correct.  The  diagrams  were  taken  to  ascertain  certain  facts,  by  the  writers 
hands  and  indicator. 


LESSON  LXXV. 


FISHKILL-LANDING  CORLISS. 

Fig.  155  was  taken  from  a  Corliss  engine,  built  by  the  Fishkill  Landing 
Machine  Company,  18  X  42  inches,  running  63  revolutions,  steam  pressure  68 
pounds,  spring  30,  heating  a  portion  of  the  mill  by  exhaust  steam.  This  dia- 
gram was  taken  from  an  engine  in  its  every-day  work,  without  making  any 
changes,  as  the  attachments  were  made  at  noon-time.  The  point  was  to  get 
at  the  average  work  of  the  engine,  as  well  as  the  load  upon  it.  Very  little 
need  be  said  of  it,  other  than  that  the  valves  of  the  engine  seem  to  be  in  ad- 
mirable condition  for  working,  although,  for  best  results,  we  would  quicken 
the  action  of  the  steam  valve  slightly  so  as  to  avoid  the  rounding  corner  be- 
tween admission  and  steam  lines,  as  well  as  to  obtain  nearer  approximation  to 
boiler  pressure,  if  possible.  The  demonstration  on  this  diagram  shows  a  very 
close  approximation  to  first-class  practice.  We  would  prefer  a  trifle  earlier 
release  so  as  to  obtain  a  little  more  compression,  but,  taken  all  in  all,  the  dia- 
gram gives  a  very  excellent  handling  of  the  steam,  and  shows  plainly  that  the 


228 


TWENTY  YEARS  WITH  THE  INDICATOR, 


valves  are  tight,  and  that  the  vibrations  in  pressure  are  taken  account  of  by 
the  indicator.  The  approximation  to  boiler  pressure  is  but  in  small  measure 
due  to  the  late  opening  of  the  steam  valve,  (61  out  of  68  pounds  are 
realized)  but  rather  to  the  crooked  steam  pipe  which  has  in  it  more 
or  less  valves,  and  through  which  steam  is  drawn  for  dyeing  as  well. 

If  the  reader  should  be  at  all  skeptical  as  to  the  absolute  necessity  of 
expressing  the  clearance  on  a  diagram  to  obtain  the  result  for  which  we  make 
the  demonstration,  let  him  add  two  per  cent,  to  the  length  of  the  diagram 
and  then  make  the  demonstration.  Some  engineers  and  others  who  have  had 
but  little  experience  with  the  matter  frequently  attempt  to  show  that  no 


FIG.  155. 

demonstration  is  correct  upon  a  diagram  without  adding  the  volume  of 
clearance,  and  whether  it  is  guessed  at  or  otherwise,  it  is  necessary.  The 
volume  of  clearance  added  to  this  particular  diagram  will  not  vary  the  ex- 
pansion line  more  than  the  width  of  it,  and  for  the  purposes  for  which  we 
make  this  demonstration  will  not  allow  the  planimeter  to  discover  any  differ- 
ence, but  if  we  are  figuring  for  the  amount  of  water  per  horse-power,  or 
steam  per  horse-power,  the  clearance  is  necessary  in  order  to  insure  the  cor- 
rectness, but  if  we  are  looking  to  show  what  a  certain  pressure  at  a  certain 
point  will  require  cut-off  at  a  certain  point,  to  accomplish  that  base  line  the 
clearance  is  no  more  necessary  in  a  computation  of  this  kind  than  is  the  read- 
ing of  a  thermometer  out-doors. 


TWENTY  YEARS  WITH  THE  INDICATOR.  229 


LESSON  LXXVI. 


AN    OCEAN     STEAMSHIP    COMPOUND    ENGINE     FITTED    WITH    CORLISS 

VALVES. 

Figs.  156  and  157  are  from  an  ocean  steamship,  fitted  with  English  en- 
gines and  English-built  Corliss  valves.  If  we  refer  first  to  156,  the  solid  line 
diagram  is  precisely  as  the  instrument  left  it.  It  is  not  a  diagram  that  is 
pleasing  to  the  eye  from  its  general  appearance  or  proportion,  nor  indeed  is 
its  mate  when  divested  of  the  test  of  its  efficiency.  These  were  pronounced 
by  several  chief  engineers  to  be  very  rough-looking  diagrams,  and  so  the  gen- 
eral reader  might  term  them  ;  but  as  we  are  dealing  not  in  proportions,  but 
for  information,  we  will  apply  the  test  and  see.  In  the  dotted  diagram  we 
have  taken  the  absolute  pressure  at  A  from  the  absolute  vacuum  line  D,  which 
we  find  to  be  54  pounds.  Upon  working  the  demonstration,  as  duly  ex- 
plained in  previous  lessons,  we  find  that  the  realized  pressure  cut  off  at  the 
point  C  E,  gives  the  actual  pressure  at  A  upon  the  proper  expansion  of  the 
steam.  The  theoretical  line  E,  which  is  drawn  dotted,  shows  plainly  that  the 
same  approximation  exists  in  the  correct  working  of  steam,  as  is  shown  from 
the  time  the  steam  valve  gets  open  at  the  commencement  of  the  diagram  up 
to  the  point  where  the  amount  of  steam  equals  the  cutting-off  at  the  point  C 
E.  The  theoretical  line  in  this  case  follows  the  actual  expansion  line  for 
quite  a  distance  so  closely  as  to  avoid  any  cause  for  criticism.  The  departure 
of  the  line  of  the  instrument  from  the  theoretical  line  shows  plainly  where  the 
valve  commenced  to  open  to  allow  the  steam  to  exhaust.  The  release  is 
very  good.  We  now  come  to  a  point  in  which  there  is  a  radical  difference 
between  the  valves  and  those  of  some  engines  which  are  shown  in  this 
volume. 

We  find  a  receiver  pressure  at  the  commencement  of  exhaust  of  five 
pounds,  the  maximum  pressure  is  between  seven  and  eight  pounds,  barely 
reaching  eight,  while  the  terminal  or  commencement  of  compression  is  about 
seven.  There  is  a  greater  difference  in  the  action  of  this  engine  witii  refer- 
ence to  the  receiver  and  the  high-pressure  cylinder  in  their  relations  to  one 
another,  than  in  that  of  almost  any  other  large  marine  engine  diagram  shown 
in  this  volume.  This  steam  line  falls  away  but  slightly,  and  we  have  an 
initial  pressure  of  plus  70  pounds,  which  falls  to  68  at  about  one-fifth  stroke, 
and  at  the  point  of  cut-off  we  have  62  pounds  out  of  70,  showing  that  the 
capacity  of  this  valve  to  furnish  steam  at  the  maximum  pressure  or  initial 
pressure,  is  almost  equal  to  fully  one-half  of  the  volume  of  the  cylinder  in 
its  steam  supply,  while  in  the  slide-valve  engines,  as  a  rule,  we  find  a 
diminution  of  pressure  varying  all  the  way  from  7  to  25  pounds  from  the 


230 


TWENTY  YEARS  WITH  THE  INDICATOR. 


initial,  and  in  some  cases  exceeding  even  that.  This  might  lead  us  to  con- 
sider whether  the  perfection  of  valve  motions  is  increasing  or  decreasing,  so 
far  as  actual  results  go,  upon  the  other  marine  engines  of  new  construction. 

It  is  a  self-evident  fact  from 
the  diagrams,  that  while  the 
compounds  may  have  ac- 
complished certain  results 
with  a  less  expenditure  of 
fuel  than  that  which  has 
previously  been  accomplish- 
ed, that  there  is  still  room 
for  a  vast  improvement  in 
the  marine  service,  over  that 
of  the  old-fashioned  beam, 
or  high  and  low-pressure 
engines,  and  whether  this 
cannot  be  carried  very  much 
further  so  as  to  compare 
with  the  best  stationary 
practice,  in  spite  of  the  dif- 
ficulties which  beset  the 
marine  service,  is  not  a 
question  upon  which  much 
discussion  can  be  had  if  the 
economic  factor  is  a  pre- 
dominant one.  This  dia- 
gram, 156,  so  far  shows  the 
highest  economic  efficiency 
of  any  marine  diagram  we 
have  yet  obtained. 

If  we  now  turn  to  Fig. 
157,  which  is  from  the  com- 
pound cylinder,  we  have 
charged  against  this  cylin- 
der the  maximum  pressure 
in  the  receiver  from  the 
high-pressure  cylinder  dia- 
gram.  It  will  be  noticed 
that  there  is  quite  a  falling 
off,  and  it  is  not  the  proper  way,  but  in  this  case  it  has  been  deemed 
preferable,  so  as  to  see  what  loss  was  incurred  from  a  possible  one,  taking 
the  initial  pressure  as  the  maximum  pressure  of  the  high-pressure  cylinder. 
If  we  take  the  realized  pressure  in  the  compound  cylinder,  it,  if  anything,  is 
carried  rather  better  as  an  approximation  to  a  straight  line  than  that  in  the 
high-pressure  cylinder,  the  reason  for  which  is  undoubtedly  a  larger  valve 
area.  The  demonstration  in  this  diagram,  taking  A  as  the  actual  pressure 


TWENTY  YEARS  WITH  THE  INDICATOR. 


231 


from  the  absolute  vacuum,  gives  us  13J  pounds,  and,  taking  the  initial  press- 
ure as  stated,  gives  the  cut-off  at  the  point  C  and  the  theoretical  line  E.  In 
this  case  the  approximation  is  exceedingly  close,  and  the  terminal  theoretical 
pressure  varies  slightly  above  the  terminal  of  the  expansion  line,  as  it  will  do 
whenever  this  basis  is  taken.  If  we  are  using  a  steam  of  lower  tension  than 

we  really  charge  in  our  com- 
putation, its  terminal  press- 
ure must  be  expected  to  be 
somewhat  above  the  terminal 
of  the  theoretical  line,  for 
volume  and  tension  must  both 
be  taken  into  account.  The 
release  in  this  case  is  not 
equal  to  that  in  the  high- 
pressure  cylinder.  The  ex- 
pansion according  to  the  theo- 
retical is  4J  pounds  below  the 
atmospheric  line,  while  the  ac- 
tual line  is  precisely  4  pounds 
below.  The  commencement 
of  the  vacuum  is  between 
eight  and  nine  pounds,  grad- 
ually running  down  to  be- 
tween ten  and  eleven  on  one 
end  and  eleven  and  twelve  on 
the  other.  The  question  may 
readily  occur  as  to  this  effect 
in  the  economy  of-  the  en- 
gine ;  in  our  own  minds  a 
vacuum  of  twenty-four  inches, 
or  twelve  pounds,  is  prefer- 
able to  one  of  twenty-seven 
or  twenty-eight ;  the  question 
has  been  often  asked  but 
never  answered,  why  should 
we  use  fifteen  or  twenty  men 
at  the  mouth  of  the  furnace 
in  throwing  in  coal,  and  a 
donkey  engine  at  the  other 

•end  of  the  engine  doing  its  level  best,  to  produce  a  temperature  of  from  freez- 
ing down  towards  zero  on  the  alternate  ends  of  the  low-pressure  cylinder, 
calling  for  its  equivalent  in  heat  at  every  filling  of  the  cylinder  with  steam  ? 
The  probability  is,  the  engineer  who  has  charge  of  this  ship  has  found  that 
he  can  run  his  feed-water  a  good  many  degrees  hotter  with  a  twenty-four 
inch  vacuum  than  with  one  which  goes  lower,  and,  we  have  no  doubt,  that  in 
that  respect  he  is  entirely  correct. 


FIG.  157. 


232  TWENTY  YEARS  WITH  THE  INDICATOR, 

There  is  another  thing  which  may  be  said  of  steam  engine  diagrams  as 
taken  from  marine  engine  cylinders.  We  have  been  allowed  to  examine  a 
great  many  steamships,  and  we  have  never  yet  seen  proper  or  fully  correct 
appliances  for  taking  of  diagrams.  Usually  the  side-pipes  are  connected  at 
the  bottom  of  the  cylinder,  a  round  turn  made  and  then  connected  on  the 
side  near  the  top.  A  three-way  cock  is  arranged  above  the  grating  and  the 
motion  is  taken  from  any  convenient  point.  The  clearance  between  the  indi- 
cator and  the  bottom  of  the  cylinder  we  have  measured  where  it  has  had 
three  times  the  distance  to  pass  upon  the  bottom  of  the  cylinder  than  on  the 
top,  for  the  steam  to  pass  from  the  engine  into  the  piston  of  the  indicator, 
and  for  that  reason  we  usually  find  the  bottom  of  most  marine  engine  dia- 
grams latest,  the  corner  most  rounded,  and  it  is  not  impossible  that  such  is 
the  case  with  156  and  157.  While  the  diagrams  show  practically  the  amount 
of  power  used,  they  show  only  an  approximation  to  the  actual  in  the  valves, 
and  the  further  removed  the  indicator  is  from  the  piston,  the  less  is  the  accurate 
working  condition  of  the  valves  shown  or  known.  These  two  diagrams  in 
156  and  157  have  a  great  many  points  of  study  for  the  practical  engineer, 
and  they  show  at  once  an  entire  difference  in  the  handling  of  the  available 
pressure,  from  that  of  most  of  the  marine  diagrams  which  are  illustrated. 
The  full  dimensions  of  the  engine  and  the  boiler  pressure  are  not  given ; 
scale  of  the  high-pressure  diagram  is  30,  that  of  the  low-pressure,  8. 


LESSON  LXXVII. 


ANOTHER  OCEAN    STEAMSHIP  COMPOUND  ENGINE. 

Quite  a  contrast  in  practice  from  the  preceding  lesson,  and  yet  one  of 
the  best  engine  results,  will  be  found  by  a  reference  to  Figs.  158  and  159, 
which  are  from  one  of  the  recently  built  steamships  with  high  and  compound 
cylinders,  the  high-pressure  being  52  inches,  compound  cylinder  93  inches  in 
diameter,  length  of  stroke  five  feet  six  inches,  revolutions  62£  per  minute, 
pressure  in  boiler  90  pounds,  scale  high-pressure  forty,  compound  twelve, 
vacuum  gauge  25,  hot  well  temperature  114°.  The  high-pressure  cylinder 
has  piston  valves,  the  compound  has  slide  valves. 

Taking  158,  our  base  line  A  shows  that  the  cut-off  occurred  at  the  inter- 
section of  C  D,  D  being  the  realized  pressure,  and  C  representing  the  volume 
of  the  cylinder  in  its  proportion  to  the  length  of  stroke  that  the  line  D  is  to 
the  whole  distance  between  the  two  extreme  vertical  lines.  The  theoretical 


TWENTY  YEARS  WITH  THE  INDICA  TOR. 


233 


curve  E  shows  that  the  loss  from  initial  pressure  to  the  point  of  cut-off  is  13 
pounds,  total  loss  from  boiler  pressure  at  the  point  of  cut-off  19  pounds  plus. 
The  theoretical  curve  follows  more  closely  than  we  would  suppose  after  it 
strikes  the  line,  running  but  very  slightly  below  it.  This  would  probably  be 
accounted  for  by  the  fact  that  the  steam  is  slightly  superheated.  The  action 
of  the  valves  in  this  case  was  very  nearly  perfect,  so  far  as  being  tight  go ; 
the  release  is  early,  and  the  counterpressure  in  the  receiver  commences  at  eleven 
pounds,  increases  to  plus  thirteen,  and  at  the  point  of  commencement  of 
compression  is  between  fourteen  and  fifteen  pounds.  The  point  at  which 
compression  ceases  and  the  steam  valve  commences  to  open,  shows  an  almost 
exactness  of  43  pounds  upon  either  end  of  the  cylinder  ;  this  is  a  point  of 
very  material  economy  in  a  quick-acting  engine  like  this,  which  is  quick-acting 
for  so  large  an  engine.  The  steam  lines  are  carried  very  well,  and  the  open- 


•f™ 


FIG.  158. 

ing  of  the  valves  is  very  nearly  right  in  both  cases.  This  is  a  desirable  im- 
provement over  that  of  some  of  the  steamships  which  still  maintain 
the  old-fashioned  slide  valve,  or  even  the  old-fashioned  piston  valve 
with  slow  speed  in  its  whole  length  of  travel.  In  this  case,  we  have 
no  doubt  the  valves  of  the  engine  are  not  based  upon  the  old-fashioned 
idea  of  valve  travel,  and  yet  there  could  be  a  radical  improvement  if  they 
were  speeded  still  higher  in  their  proportion  of  travel  to  that  of  the  piston 
of  the  engine.  Possibly  a  little  increase  of  travel  would  aid  it. 

In  diagram  159,  we  have  again  charged  the  engine  with  the  full  amount 
of  the  maximum  pressure  in  the  receiver.  One  end  has  13  pounds  plus  for  its 
initial,  while  the  other  end  only  gets  11  pounds,  and  it  will  be  noticed  that 
the  end  upon  which  we  have  erected  the  demonstration,  the  main  valve  is  con- 
siderably later  than  on  the  other  end.  This,  without  any  doubt,  accounts  for 


234 


TWENTY  YEARS  WITH  THE  INDICATOR. 


a  portion  of  this  change,  and  the  contrast,  as  between  the  admission  and 
carrying  of  steain  in  the  two  diagrams,  shows  the  most  radical  difference 
between  that  of  158,  the  fact  being  158  is  piston  and  159  slide  valves.  The 
opening  and  closure  of  valves  in  159  show  plainly  that  they  are  very  slow  in 
both  motions,  whether  the  passage  ways  are  sufficient  or  not  can  only  be  told 
by  actual  demonstration  from  measurement,  but  it  is  a  self-evident  fact  from 
the  indicator,  that  the  admission  of  steam  on  the  left-hand  diagram  of  159  is 
exceedingly  slow.  The  valve  is  also  slow  in  its  motion,  and  the  pressure 
drops  away  much  faster  than  on  the  other  end  of  the  same  cylinder.  This  is 
sometimes  accomplished  by  having  the  valves  so  balanced  for  opening  that 
the  real  travel  of  the  valve  never  reaches  wide  open  on  that  end,  while  upon 
the  other  end  of  the  cylinder  the  valve,  having  been  cast  solid  and  finished, 
had  a  travel  which  may  be  slightly  earlier  in  its  opening,  and,  owing  to  the 
angularity  of  the  rod,  quicker  in  its  movement.  In  this  case  the  theoretical 


FIG.  159. 

curve  follows  closely,  after  the  actual  line  of  the  instrument  and  the  theoreti- 
cal curve  meet.  In  this  case,  our  demonstration  base  A  shows  an  actual 
pressure  at  the  very  point  of  crossing  the  atmospheric  line  of  14.7  plus  above 
absolute  vacuum.  The  line  D  represents  the  maximum  receiver  pressure,  and 
the  working  out  of  the  two  problems  on  the  base  line  A  gjves  the  point  C  on 
D,  from  which  the  quantity  of  steam  at  the  pressure  of  D  should  have  been 
cut  off  to  furnish  the  pressure  at  A  ;  and  in  the  computation  for  power  or  fuel 
consumption,  the  amount  of  steam  used  between  the  valve's  opening  and 
closing,  was  equivalent  to  the  pressure  cut  off  at  C  on  D,  so  that  while  the 
valve  was  not  closed  at  C,  its  closing  was  equivalent  to  an  increased  pressure, 
and  a  diminished  volume  of  the  cylinder  filled  at  that  pressure  to  accomplish 
what  was  done  at  A.  The  release  on  both  diagrams  is  very  good,  generally 
considered,  but  the  right-hand  end  diagram  seems  to  have  some  kind  of  a 
struggle  going  on  which  makes  a  curiously-shaped  expansion  line,  or  in  the 


TWENTY  YEARS  WITH  THE  INDICATOR. 


235 


closure  of  the  valve  evidently  causes  some  vibration  in  the  pressure  which  is 
not  fully  accounted  for.  The  solid-lined  diagram  commences  with  9  pounds 
of  vacuum,  runs  down  to  plus  11  pounds,  compresses  on  about  12  pounds, 
and  takes  steam  about  the  crossing  of  the  atmospheric  line.  The  other  end 
of  the  cylinder  commences  its  vacuum  at  about  10  pounds,  running  down  to 
plus  12,  as  it  could  readily  do  from  the  less  amount  of  steam  used  upon  that 
end  of  the  cylinder. 

The  two  diagrams,  158  and  159,  were  taken  by  a  Thompson  indicator  in 
order  to  ascertain  the  exact  power,  and  as  nearly  as  possible  the  position  of 
the  valves.  It  would  be  very  interesting  if  short  connections,  and  a  posi- 
tively correct  motion  could  be  arranged  for  this  pair  of  engines,  to  get  at  the 
facts  with  reference  to  the  actual  position  of  the  valves  from  a  close  connec- 
tion to  the  cylinder,  and  the  closest  approximation  to  a  positive  and  correct 
motion  for  the  instrument. 


LESSON  LXXVIII. 


CONDENSING  CARRIED  BEYOND  ITS  ECONOMICAL  APPLICATION. 

In  Fig.  160  we  have  an  old  Corliss  engine,  which  has  been  running  night 
and  day  for  a  number  of  years,  twenty- 
two  inches  diameter,  forty-eight  inch 
stroke,  running  500  feet  per  minute 
piston  speed,  independent  condenser, 
twenty-four  spring.  In  this  case  the 
amount  of  steam  actually  used  by  the 
engine  is  represented  by  the  line  A,  one 
end  of  which  touches  the  admission  line, 
and  the  other  the  dotted  line,  which  is 
the  boundary  of  the  proportion  of  the 
cylinder  filled  with  steam.  The  demon- 
stration is  made  from  the  line  of 


FIG.  ;60. 


236  TWENTY  YEARS  WITH  THE  INDICATOR. 

pressure  F.  Apparently  the  engine  cuts  off  very  much  shorter  than  where 
the  dotted  line  is  drawn,  but  upon  the  demonstration  we  follow  down  the 
dotted  corners  of  where  the  ordinates  cross  the  lines,  forming  the  boundary 
of  the  theoretical  curve.  At  B  we  find  that  the  line  of  the  indicator  or  actual 
is  below  the  theoretical,  at  C  the  actual  line  is  but  very  triflingly  below.  Now 
what  happens  between  A  and  B,  or  B  and  C  I  Nothing  more  or  less  than 
that  the  valve  does  not  close  tight,  or  else  that  it  leaks  after  having  closed 
and  before  it  is  firmly  seated.  From  C  to  D  the  steam  continues  to  come  in ; 
at  E  the  expansion  line  is  below  the  theoretical  and  it  shows  to  the  eye,  com- 
paratively, that  the  line  drops.  It  is  undoubtedly  caused  by  the  much  more 
rapid  expansion  of  the  steam.  At  F  the  lines  are  together,  and  so  on,  getting 
a  trifle  above  before  the  end  of  the  stroke.  There  are  several  points  about 
this  worthy  of  notice,  the  first,  that  the  expansion  line  is  somewhat  irregular, 
and  the  second  is  that  the  drifting  which  occurs  from  one  point  to  the  other 
is  fully  proved  by  the  location  of  the  theoretical  and  the  actual  lines.  The 
vacuum,  in  this  case,  reaches  nearly  twelve  pounds,  or  twenty-four  inches ; 
very  many  of  our  oldest  engineers,  who  run  condensing  or  compound,  claim 
that  at  this  point  it  is  by  far  the  most  economical,  as  the  temperature  of  the 
water  at  this  particular  point  is  much  more  advantageous  for  re-use  or  for 
feeding  than  as  though  more  vacuum  was  obtained.  The  high  range  of  change 
of  temperature  between  even  the  terminal  pressure  of  3  or  5  pounds  pressure 
and  12  to  14  pounds  of  vacuum  makes  a  tremendous  waste  of  live  steam  by 
condensation,  and  a  moderate  vacuum  and  hot  feed  water  use  less  coal  to 
produce  the  same  amount  of  indicated  horse-power,  other  things  being  equal. 
We  believe  this  position  is  tenable  ;  however,  it  is  a  point  for  argument,  and 
engineers  who  wish  to  do  so  may  find  food  for  figures  drawn  from  actual  ex- 
perience, in  case  they  take  it  up,  putting  any  experience  they  may  have  in 
connection  with  the  facts. 

There  is  another  point  about  this  diagram  which  we  have  not  elaborated 
on,  that  is,  the  reference  of  the  area  between  the  high-pressure  and  condens- 
ing, the  relation  of  one  to  the  other.  The  question  is,  does  this  engine  do  as 
well  as  though  it  carried  steam  a  little  further  at  a  less  pressure  or  not  ? 
There  is  not  the  least  doubt  that  in  many  cases  engines  are  underloaded,  and, 
"to  save  coal,"  the  condenser  is  added,  and  more  coal  used  with  a  condenser 
than  without  it ;  the  reason  is  not  far  to  seek.  A  small  quantity  of  steam 
raises  the  heat  but  little,  and  it  is  easier  to  maintain  14  pounds  vacuum  on  a 
small  amount  of  steam,  and  the  cylinders  are  refrigerators  to  a  greater  extent 
than  the  point  of  economy. 


TWENTY  "YEARS  WITH  THE  INDICATOR. 


LESSON  LXXIX. 


AN    OLD    CORLISS    ENGINE,     ACTUAL    COST    OF    A    HORSE-POWER    PER 

HOUR. 

In  Fig.  161  we  have  a  Corliss  engine  which  has  been  running  a  number 

of  years,   twenty   inches   diameter,    60-inch 

stroke,  sixty-three  revolutions  per  minute, 
fifty-five  pounds  boiler  pressure,  throttle 
valve  wide  open,  forty  spring,  Thompson 
improved  indicator,  not  quite  the  whole 
amount  of  work  on.  Both  ends  are  shown. 
We  have  made  a  demonstration  only  upon 
one  end  for  the  purpose  of  finding  out  how 
the  engine  was  running.  These  diagrams 
were  taken  with  a  three-way  cock,  or  by 
changing  from  one  end  to  the  other.  In 
either  case,  we  have  demonstrated  from  the 
diagram  coming  nearest  the  boiler  pressure, 
and  it  shows  a  beautiful  working  of  steam, 
A  line  of  boiler  pressure,  B  atmospheric 
line,  C  vacuum,  D  volume  of  cylinder  filled 
with  steam  at  boiler  pressure  to  do  the 
work,  cutting  off  at  E,  or  at  the  intersection 
of  the  lines  A,  D.  The  theoretical  line  is 
dotted  down  to  the  point  where  it  runs  into 
the  actual  line  of  the  instrument,  which  is 
considerable  of  a  distance  above  the  point 
assumed  for  the  base  line.  It  then  "follows 
so  closely  that  we  have  used  our  old  method 
again  of  dotting  the  intersection  of  the  lines 
in  the  demonstration.  There  may  be  a  slight 
difference  in  the  terminal  of  this  diagram, 
for  the  original  was  very  faintly  drawn  and 
was  traced  over  by  hand.  The  steam  line  is 
extremely  good  on  the  right-hand  diagram  ; 
the  one  on  the  left  falls  off  considerably,  and 
the  pressure  would  seem  to  have  changed 
between  the  time  of  taking  the  two  ends. 
The  vacuum  in  this  case  realizes  about  ten 


FIG.  161. 


pounds.     The   diagram  was  taken  August   4,   and  we  could  hardly  expect 
much    more  than   ten  pounds,    or   twenty  inches,   at   that    time    of  year. 


238  TWENTY  YEARS  WITH  THE  INDICATOR. 

Taken  all  in  all,  it  is  an  excellent  diagram.  There  is  in  this  case  no 
leakage  anywhere  that  we  can  find.  The  admission  line,  steam  line,  ex- 
pansion, are  all  good.  If  we  were  to  change  anything  it  would  be  an 
earlier  release  and  a  trifle  more  compression,  and  it  is  possible  we  might  ob- 
tain a  little  more  vacuum  by  so  doing.  At  the  time  of  taking,  a  portion  of 
the  machinery  of  this  mill  was  stopped.  There  are  some  figures  accompany- 
ing this  which  will  interest  steam  users.  The  power  of  the  engine,  f our  times 
per  day,  six  days  per  week,  averages  151-horse.  The  fuel  used  is  three- 
fourths  anthracite  coal  dust  from  city  coal  yards,  and  one-fourth  Clearfield 
coal.  The  cost  of  this  fuel  is.  as  follows :  Clearfield  $3.30,  and  anthracite 
dust  $1.80  per  ton  of  2000  pounds,  in  the  coal  house  ;  sixty-six  hours'  use, 
17,110  pounds  of  dust,  5,622  pounds  of  Clearfield,  making  22,732  pounds, 
costing  $25.80  ;  average  power,  151-horse.  The  diagrams  were  taken  twice 
in  the  forenoon,  twice  in  the  afternoon,  and  the  average  of  twenty-four  cards 
in  the  week  taken  for  the  amount  of  power.  Pounds  of  coal  per  hour,  344  ; 
pounds  of  coal  per  horse-power  per  hour,  2.28  ;  cost  of  151  horse-power  per 
hour,  00.39  ;  cost  of  one  horse-power  one  hour,  .00259.  Three  horizontal, 
tubular  boilers  are  in  use,  6  X 16  feet. 

Two  boilers  are  used  in  the  summer,  three  in  the  winter.  The  fireman  is 
not  allowed  to  use  a  slice  bar  any  time  during  the  day,  but  when  the  fires  are 
banked  at  night  they  are  cleaned.  The  inside  of  the  chimney  is  equal  to  the 
full  area  of  all  the  tubes  in  the  three  boilers,  and  106  feet  high,  and  the  flue 
from  the  boiler  to  the  chimney  is  a  little  larger  than  the  full  area  of  the  tubes 
in  the  boiler.  Ash-pit  doors  are  never  closed  when  the  boilers  are  running. 
The  mills  started  nearly  two  years  ago,  and  the  grates  are  as  straight  as 
when  they  were  put  into  the- furnace.  The  agent  is  a  close  student  of  the 
indicator,  has  profited  by  his  experience,  and  bought  a  new  Thompson  Im- 
proved for  his  engineer,  and,  on  condition  that  we  will  not  refer  parties  to 
him,  has  given  us  permission  to  state  the  facts  in  connection,  and  also  that  his 
engineers  and  firemen  are  well  paid,  and  take  just  as  much  interest  in  the 
economic  handling  of  the  engine  and  boilers  as  he  does  himself.  We  might, 
perhaps,  say  that  this  engine  was  wanted  in  a  hurry,  and  was  second-hand 
before  it  went  into  this  mill,  having  been  replaced  by  a  very  much  larger  one. 
It  was  overhauled,  and  this  is  its  record. 


NOTE. — The  cost  of  an  I.  H.  P.,  in  anything  but  fractions  of  a  cent  per  hour,  should 
not  be  allowed ;  pounds  of  coal  per  I.  H.  P.  per  hour  is  a  meaningless  and  indefinite 
term. 


TWENTY  YEARS,  WITH  THE  INDICATOR. 


LESSON  LXXX. 


WHAT  AN  OVERLOADED  CORLISS   ENGINE  CAN    DO— SOME   OF  THE 
GENERAL  DEFECTS  OF  ARRANGEMENT, 

The  diagrams  with  this  are  from  a  Watts,  Campbell  &  Co.  Corliss  engine, 
and  we  have  laid  aside  anything  that  is  theoretical  or  supposed,  taking  only 
visible  facts.  And  this  shows  one  of  the  instances  which  are  constantly 
coming  to  the  notice  of  the  engineer  who  has  any  indicating  to  do,  of  the  ne- 
cessity of  simultaneous  diagrams  for  adjustment  of  valves,  or  for  reliable  data 
with  reference  to  power  exerted. 


^ £ -/:-• 


FIG.  162. 

The  diagrams  in  this  case  were  taken  on  each  end  of  the  cylinder  ;  A  is 
the  line  of  boiler  pressure  at  the  instant  the  diagram  was  taken,  the  scale 
being  forty.  B,  B'  represent  the  visible  point  of  cut-off,  simply  for  com- 
parison. C,  C'  are  the  respective  lines  of  initial  pressure  above  the  atmos- 
pheric line,  or  the  instrument  at  rest.  D,  D'  show  the  lowest  pressure  from 
initial  realized,  and  E  shows  what  went  on  occasionally  while  one  end  was 
trying  to  catch  up  with  or  do  as  much  as  the  other.  These  lines,  simple  in 
themselves,  are  full  of  meaning  and  will  bear  a  little  investigation. 

The  engine  at  this  time  was  in  the  course  of  adjustment  for  the  position 
of  the  valves  to  obtain  the  best  possible  results.  The  diagrams  H  and  C  were 
taken  on  the  very  same  strokes  of  the  engine,  but  we  have  not  drawn  in  all 
the  fluctuations  caused  by  the  reaching  of  the  governor,  first  to  increase  for 
one  end  and  then  to  diminish  the  cut-off  cams'  action  for  the  other.  We  have 
here  a  boiler  pressure  of  eighty-two  pounds,  a  realized  pressure  of  sixty-four 
pounds,  a  supply  pipe  of  2  J  or  3  inches  diameter  for  a  cylinder  of  14  X  32 


2io  TWENTY  YEARS  WITH  THE  INDICATOR, 

inches  running  80  to  88  revolutions.  The  H  end  diagram  in  this  case  meas- 
ures 391  on  the  planimeter,  the  C  end  measures  328.  The  line  E  occurred 
on  every  single  diagram  that  was  taken  until  after  the  two  ends  were  bal- 
anced. In  this  case  391  equals  79.5  horse-power,  328  equals  67.6  horse- 
power, so  that  on  a  load  of  80  horse-power  we  have  a  variation  of  about 
twelve  horse-power  between  the  H  and  C  ends  on  the  same  stroke,  or  almost 
sixteen  per  cent.  It  will  be  noticed  that  the  terminal  pressure  of  the  head 
end  is  seventeen  pounds,  the  terminal  pressure  of  the  crank  end  is  thirteen 
pounds,  while  the  terminal  pressure  of  the  crank  end  when  it  makes  a  jump, 
as  in  the  case  of  the  diagram  E,  is  33^  pounds.  The  loss  in  the  first  place 
eighteen  pounds  between  boiler  pressure  and  the  highest  realized  pressure  on 
the  head  end.  A  loss  is  also  made  from  the  moment  the  valves  open  until 
they  cut-off  of  ten  pounds  more  on  the  head  end,  between  realized  initial  and 
the  pressure  at  cutting  off,  making  twenty-eight  pounds  below  boiler  press- 
ure, or  a  little  over  one-third  of  the  steam  pressure  to  start  with  on  the  ex- 
pansion line.  On  the  crank  end  a  loss  of  twenty  pounds  between  boiler  and 
highest  initial  and  eight  pounds  between  highest  initial  and  at  point  of  cut- 
off. By  a  curious  coincidence  both  ends  cut  off  at  about  the  same  loss  of 
pressure  although  at  different  lengths.  The  crank  end  carries  steam  equiv- 
alent to  about  13  J,  as  compared  with  the  head  end  carrying  18,  call  it  inches 
only  for  comparison.  Most  of  these  diagrams  show  the  racing  of  the  gover- 
nor up  and  down  with  every  stroke  of  the  engine,  endeavoring  in  every  in- 
stance after  the  valve  had  been  set  for  the  head  to  get  around  quick  enough 
to  set  the  valve  for  the  crank ;  in  this  case  very  wide  variations  were  the 
consequence,  and,  in  the  particular  diagram  which  we  have  engraved,  only 
three  lines  were  made  in  order  to  catch  carrying  steam  at  three-quarters 
stroke.  Wherever  more  than  four  or  five  strokes  of  the  engine  were  made 
upon  the  indicator  card  we  find  this  carrying  nearly  full  stroke  on  every  one, 
so  that  about  one  line  in  four,  or  five,  the  regulator  jumped  to  catch  the  crank 
end  with  the  head  end.  Good  engineers  will  understand  this  at  once.  The 
changing  of  the  governor  is  continual  and  about  once  in  so  many  strokes  it 
will  set  a  little  further  than  is  necessary  and  skip  tripping  the  valve.  All  en- 
gineers will  also  see  that  this  is  an  exceedingly  dangerous  practice ;  there  is  a 
great  deal  of  force  exerted  as  between  60  and  100  horse-power,  when  it  is  only 
for  a  single  stroke  of  the  engine,  and  something  has  to  withstand  that  power 
or  else  the  engine  would  smash. 

There  is  another  peculiarity  in  this  case  ;  it  will  be  noticed  that  the  crank 
valve  is  very  nearly  in  position  so  far  as  the  admission  line  is  concerned,  while 
the  head  valve  shows  plainly  where  the  cushion  terminates  and  the  admission 
line  commences  ;  also  that  the  admission  line  leans  away  to  the  right  from  the 
vertical  line.  This  engine  had  only  one  screw  in  the  jim-crank  of  the  main 
steam  valves,  and  the  thread  which  connected  the  crab-claw  with  the  iron  stem 
was  so  coarse  that  a  whole  turn  was  too  much,  and  nothing  less  than  a  whole 
turn  could  be  given  in  adjustment,  which  is  not  the  case  with  larger  size 
engines.  The  eccentric  having  been  put  right  for  three  valves,  and  the  same 
difficulty  existing  on  the  crank  valve,  we  were  compelled  to  leave  it  a  little 


TWENTY  YEARS  WITH  THE  INDICATOR.  241 

late  oil  the  admission  line  ;  for  had  we  changed  it  again  on  the  main  rod,  it 
would  have  thrown  the  crank  valve  just  as  much  forward  or  backward,  leaving 
us  with  only  a  whole  turn  to  adjust  with.  This  practice  of  having  right  and 
left  threads  on  both  ends  of  the  exhaust  and  steam  valve  connections,  to  give 
nicety  of  adjustment  should  be  insisted  on  by  engineers  in  new  engines. 

If  the  readers  will  figure  the  pounds  exerted  between  79.5  horse-power 
on  one  end  and  67.6  on  the  other,  they  will  find  that  there  is  a  very  great 
change  of  force  exerted  between  the  different  strokes  and  as  many  strokes  as 
are  made  in  each  minute,  which  is  not  at  all  to  the  benefit  of  the  engine. 
There  are  very  many  other  points  connected  with  these  simultaneous  dia- 
grams, but  leaving  all  but  the  practical,  we  find  enough  to  encounter  to  draw 
our  attention  to  the  fact  that  it  is  very  necessary  to  use  both  indicators,  if  we 
are  getting  either  the  power  correctly,  the  variations  in  power  or  the  position 
of  the  valves.  It  is  an  interesting  study  and  more  interesting  in  the  practice. 
It  will  be  noticed  on  the  crank  end  that  the  exhaust  is  a  little  late  on  the 
small  diagram,  and  that  the  same  feature  is  very  evident  in  the  larger  one. 
The  small  amount  of  power  exhausts  under  a  start  of  about  five  pounds,  while 
the  jump  to  nearly  whole  stroke  exhausts  under  twenty- two  or  twenty-three 
pounds  back  pressure  at  the  beginning  of  the  return  stroke.  There  are  sev- 
eral interesting  features  which  will  be  borne  out  if  a  little  examination  is 
given,  and  will  prove  all  the  more  interesting. 

This  is  one  of  the  troublesome  things  to  engineers,  running  from  50  to 
100  H.  P.  regularly  on  a  60  H.  P.  machine.  Some  of  the  full  load  diagrams 
on  this  engine  show  102  H.  P.,  the  builders  did  not  apply  the  small  feed- 
pipe, or  arrange  the  engine  to  carry  full  stroke. 


LESSON  LXXXI. 


AN    OCEAN   COMPOUND. 

Figs.  163  and  164  were  taken  nearly  three  years  since,  from  a  then  new 
ocean  steamer  ;  163  is  scale  32  per  inch  ;  164,  12  per  inch.  The  difference 
which  is  shown  between  the  different  ends  of  the  cylinder  show  a  trifle  less 
than  300  horse-power  difference  between  the  left  and  the  right-hand  card. 
Taking  A  and  A'  as  the  base  lines,  we  find  the  point  of  cut-off  at  B,  B',  from 
each  of  which  points  the  theoretical  line  is  drawn,  taking  the  cylinder  as  realiz- 
ing boiler  pressure.  The  expansion  line  upon  one  end  is  somewhat  peculiar, 


242 


TWENTY  YEARS  WITH  THE  INDICATOR. 


but  closely  follows  the  theoretical  with  a  little  difference,  which  will  be  ac- 
counted for,  as  between  realized  and  boiler  pressure.  Upon  the  other  end 
we  have  a  different  account ;  the  steam  enters  the  cylinder  and  immediately 
falls  away  in  pressure,  so  that  at  B'  ten  pounds  of  pressure  is  lost  between 
the  initial  and  the  point  of  cut-off,  allowing  six  pounds  for  lost  boiler  pressure 

equivalent  to  equal  to  the 
other  end.  There  is  a 
reason  for  this.  The  left- 
hand  card  is  from  the  top 
of  the  cylinder  where  the 
distance  from  the  steam 
way  to  the  indicator  cock 
is  less  than  one  foot,  while 
the  other  end  is  taken 
from  the  bottom  of  the 
cylinder  through  a  steam 
pipe  more  than  five  feet 
long.  It  is  probable  that 
the  left-hand  diagram  is 
much  nearer  the  fact  than 
the  right-hand  one,  and 
that  quite  a  difference  in 
the  horse-power  would  be 
developed  if  both  these 
connections  were  made 
short,  and  two  indicators, 
instead  of  one,  were  used. 
The  release  of  this  engine 
is  very  good.  We  find 
the  commencement  of  ex- 
haust on  one  end  with  7 
pounds  receiver  pressure, 
and  only  a  trifle  more 
than  7  on  the  other;  the 
maximum  pressure  is  12 
pounds.  Quite  a  varia- 
tion occurs  in  compres- 


FIG.  163. 


sion,  and  if  the  difference 
exists  in  proportion  to  the 

length  of  pipe  connection  that  is  shown  in  the  compression  on  the  two 
diagrams,  then  the  left-hand  diagram  has  a  square  steam  corner,  and  the 
right-hand  one  comes  honestly  by  the  little  hump  at  the  commencement  of 
the  steam  line.  All  these  diagrams  for  that  matter  are  only  approximately 
correct,  on  account  of  this  very  crude  way  of  establishing  the  indicator 
connections  between  the  top  and  bottom. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


243 


line   then  falls  off   from   re- 
pressure    almost   8   pounds. 


Turning  to  Fig.  164,  we  have  a  most  peculiar  train  of  circumstances. 
These  diagrams  were  taken  with  a  12  scale.  We  have  only  drawn  the  theo- 
retical curve  upon  one  end,  as  that  answers  every  purpose  for  comparison  of 
the  diagram.  We  first  charge  the  engine  with  the  full  amount  of  receiver 

pressure,  viz.,  12  pounds;  it  will  be 
seen  that  the  opening  of  the  valve  is 
such  that  a  little  kick  occurs  in  the 
opening  action  of  the  indicator.  The 
steam 
ceiver 

We  have  drawn  the  line  D  where  the 
two  steam  lines  of  the  diagram  cross 
each  other,  and  we  find  there  a  loss 
of  plus  7  on  one  and  about  8  pounds 
on  the  other  end.  But,  to  give  the 
engine  credit,  we  have  drawn  the 
line  B  on  one  side  and  B'  on  the 
other  as  about  the  average  of  the 
realized  pressure  initial,  and  what 
the  engine  should  have  done  if 
either  end  of  the  compound  cylinder 
had  have  worked  as  well  as  the  left- 
hand  of  the  high-pressure.  The  line 
F  is  the  line  of  the  instrument,  B  is 
the  line  of  initial  pressure,  C  equals 
the  volume  of  the  cylinder  filled  or 
the  point  ol  cut-off,  E  the  theoretical 
line  drawn  from  the  base  line  A.  The 
steam  in  the  cylinder  if  it  had  fol- 
lowed the  line  B  up  to  the  point  C, 
and  then  the  theoretical  line  would 
have  yielded  almost  200  horse-power 
more  than  it  does  do  ;  the  actual 
amount  of  the  card  shown  is  1474.8 
horse-power,  while  had  it  have  real- 
ized the  pressure  B  to  the  point 
C  and  the  expansion  line,  with  the 
same  vacuum,  it  would  have  yielded 
1662.9  horse-power.  We  find  that 
neither  end  of  the  compound  cylinder  accomplished  as  much  work  as 
the  high-pressure,  and  that  there  is  a  more  radical  difference  in  the  actually 
developed  power  in  the  high-pressure  cylinder,  than  in  the  low.  The  results 
in  this  case  may  be  of  interest  to  our  readers.  The  steamship,  from  whose 
engines  these  diagrams  were  taken,  made  three  round  trips,  (he  engines  were 
very  largely  altered  and  very  much  improved,  as  they  would  need  to  be  from 
the  apparent  action  shown,  from  the  very  great  differences  which  exist 


FIG.  164. 


244  TWENTY  YEARS  WITH  THE  INDICATOR. 

in  both  high  and  low-pressure  cylinder,  from  first-class  practices.  These 
things  are  not  visionary,  theoretical,  or  supposable ;  it  is  only  a  matter 
of  fact  that  they  do  exist  as  they  do,  and  that  it  is  so  expensive  a  matter  when 
such  results  as  these  are  carefully  figured  out,  to  make  a  change  in  an  engine, 
or  abolish  them  entirely. 


LESSON  LXXXH. 


DEFECTIVE   CONSTRUCTION,    AND  AN   INCIDENT  IN  THE   USE  OF  THE 

PANTOGRAPH. 

This  lesson,  with  the  exception  of  the  Harris-Corliss  diagram,  shows 
radical  defects  in  construction,  in  usage  and  in  the  application  of  the  indi- 
cator, and  it  is  quite  as  necessary  that  the  readers  of  this  volume  should 
know  where  to  look  for  difficulties  and  how  to  avoid  them,  as  it  is  to  know 
the  theory  of  doing  a  thing  right  without  having  the  practical  results  before 
them. 

Figs.  165  and  166  were  both  taken  from  the  same  engine.  The  engine 
was  of  peculiar  construction,  and  had  been  subject  to  several  examinations 
and  alterations,  the  warranty  being,  as  is  frequently  the  case,  that  it  should 
equal  the  Corliss  engine  in  economy,  development  and  regulation.  As  the 
readers  of  this  volume  will  have  plenty  of  Corliss  material  with  which  to  com- 
pare, they  must  form  their  own  inferences  or  deductions,  we  have  only  to  nar- 
rate the  facts.  The  engine  in  question  was  built  for  a  speed  of  80  revolutions 
per  minute ;  it  was  well  located,  well  connected,  but  for  some  reason  it  had 
not  given  satisfaction  to  its  owners. 

Fig.  165  is  an  actual  diagram  with  the  simple  addition  of  absolute 
vacuum,  the  base  line  and  the  theoretical  curve,  with  a  portion  of  the 
initial  or  realized  pressure  line  added,  in  order  to  show  that  after  the  valve 
commenced  to  open,  the  pressure  in  the  cylinder  considerably  increased,  and 
instantly  commenced  to  decrease  perceptibly  before  the  point  of  cut-off,  which 
we  have  termed  visible,  occurred.  The  expansion  line  would  seem  to  show 
a  very  fair  action  both  of  the  indicator  and  steam,  and  without  the  theoreti- 
cal curve,  (with  the  exception  of  the  joining  of  the  admission  and  steam  lines, 
and  the  little  irregularities  in  that  line  as  well  as  in  the  compression)  it 
would  seem  to  be  a  pretty  good  diagram.  But  when  we  apply  the  base  line, 
to  learn  from  it  the  point  of  cut-off  and  that  one  point  of  the  theoretical 
curve  quite  corroborates  the  other  with  regard  to  the  amount  of  steam  used, 
it  becomes  less  pleasant  than  on  its  first  impression. 


TWENTY  YEARS  WITH  THE  INDICATOR. 


245 


Fig.  165  was  taken  at  a  speed  of  80  revolutions  ;  the  peculiarities  of  the 
diagram  will  be  explained  later.  Fig.  166  was  taken  from  the  same  engine 
during  the  same  trial  or  observation,  and  at  a  moment  when  the  speed  of  the 
engine  had  reached  124  revolutions  per  minute.  The  peculiarities  in  this  are 
that  the  same  general  features  which  occurred  in  165  are  present,  both  in  the 
compression  and  steam  lines,  and  that  the  serrations  or  irregularity  of  the 
steam  line  is  increased  very  much  more  by  the  high  speed  than  it  is  by  the 
usual  speed  of  the  engine.  It  will  be  seen  also  that  the  point  of  cut-off  is 
quite  different  from  that  of  the  previous  diagram,  or  165,  but  that  there  still 
remains  this  extreme  leak,  and  that  both  points  on  the  theoretical  line,  initial 
and  terminal  pressure,  corroborate  the  previous  reading.  Fig.  165  figures  by 
the  planimeter  10.1  horse-power;  Fig.  166  figures  10.2  horse-power.,  at  the 
different  speeds  at  which  they  were  running,  at  the  moment  of  taking.  It  will 

be  noticed  that  the  steam  line  in  both 
these  diagrams  shows  almost  a  parallel 
line  with  the  vertical  at  that  end.  This 
engine  had  been  carefully  examined  by  an 
old  engineer,  who  had  indicated  it  and 
reported  upon  it ;  the  report  was  very 
favorable  indeed.  The  facts  in  the  case 
are  as  follows :  The  two  diagrams,  165 
and  166,  show  a  variation  of  revolutions, 
44,  per  minute  ;  during  the  time  of  the 


FIG.   165. 

trial,  the  engine  ran  from  68  to  124,  and  there  was  connected  with  it 
an  attachment  for  showing  the  variation  in  speed,  which  during  the  time 
ran  completely  off  the  paper  band,  without  making  the  least  mark;  so 
much  for  the  facts  with  reference  to  the  regulation.  During  the  time 
of  trial,  which  extended  over  some  thirteen  hours,  we  applied  the  theo- 
retical curve,  and  were  somewhat  surprised.  When  the  finish  of  the  test  was 
made,  the  manager  was  called  upon  to  make  some  examinations  (which  had 
been  quietly  made  the  night  before,  but  without  any  proof).  His  attention 
was  called  to  the  fact  that  the  piston  traveled  over  the  indicator  plug  holes 
at  both  ends  of  the  cylinder,  so  that,  as  a  matter  of  fact,  the  diagrams 
were  perfectly  worthless  in  regard  to  their  steam  lines  and  admission  lines ; 
the  expansion  line  is,  however,  fully  corroborated  by  admitting  steam  to  the 
chest  while  the  valves  were  unhooked  from  the  eccentric,  and  such  a  jet  of 
steam  as  came  through  the  indicator  plug  holes  has  only  been  seen  by  those 
who  have  found  valves  which  leak  badly.  In  the  case  of  165,  the  steam  line 


246  TWENTY  YEARS  WITH  THE  INDICATOR. 

approximates  closely  to  a  parallel  line,  but  when  the  piston  moves  back  so 
that  the  indicator  hole  is  uncovered,  the  steam  is  admitted  more  and  more 
into  the  indicator,  giving  a  triflingly  higher  pressure  just  as  the  movement  for 
the  cut-off  begins  to  take  effect.  The  compression  plainly  shows  that  some- 
thing goes  on  beyond  it,  and  whatever  amount  of  space  may  lie  beyond  that 
covered  by  the  indicator  hole  we  know  nothing  of,  for  no  changes  could  be 
made,  or  we  would  promptly  have  made  a  clearance  with  a  cold  chisel  or 
drill. 

Fig.  166  shows  the  admission  while  the  engine  was  racing,  and  simply 
magnifies  what  is  plainly  seen  in  165  in  a  smaller  degree.  The  expansion 
line  in  both  cases,  without  the  theoretical,  would  give  an  idea  of  a  good  line. 


FIG.  166. 

But,  taking  the  actual  pressure  at  the  base  line  of  the  demonstration,  we  find 
there  is  entirely  too  much  pressure  for  the  steam  and  volume  cut-off  as  by 
the  visible  point  of  cut-off  on  the  diagram.  We  also  find  a  corroboration  of 
this  in  the  fact  that  the  theoretical  line  runs  below  the  actual  line,  and 
the  terminal  pressure  is  as  much  too  high  in  proportion  as  the  absolute 
pressure  is  at  the  point  of  the  base  line.  We  were  told  some  months  after 
that  the  price  of  this  engine  had  more  than  been  paid  by  the  damage  it  had 
done  to  the  place  it  was  working  in,  which  would  seem  to  corroborate  the 
indicator's  work  to  the  extent  of  wasting  the  steam,  and  also  the  fact  that 
the  regulation  was  exceedingly  far  from  that  of  the  average-built  Corliss 
steam  engine.  These  two  diagrams,  165  and  166,  are  well  worthy  the  careful 
study  of  every  engineer  who  desires  to  know  something  further  as  to  the 
reliability  of  the  indicator.  Both  diagrams  were  taken  with  a  30  scale. 


TWENTY  YEARS  WITH  THE  INDICATOR.  247 


AN  INCIDENT. 

Fig.  167  is  from  a  Harris-Corliss  engine  slightly  thrcitled,  scale  40,  and 
the  only  remarkable  feature  about  this  is  the  peculiar  twist  in  the  expansion 
line,  something  which  very  rarely  occurs.  This  occurred  a  number  of 
times  while  the  author  was  busy  in  changing  the  valves,  eccentrics,  cranks, 
etc.,  and  was  really  quite  a  puzzle  until  particular  attention  was  given  to 
what  made  it.  The  result  of  an  examination  proved  that  the  cord  which  led 
from  the  indicator  to  the  pantograph  motion,  which  was  being  used,  struck 
apon  the  top  of  the  slotted  screw  next  to  the  post  to  which  our  strings  were 
attached,  in  such  a  way  that  a  snap  was  given  to  the  cord  both  ways,  sud- 
denly changing  the  speed  of  the  paper  barrel  first  above  and  then  below, 
until  this  slot-headed  screw,  in  the  forward  and  backward  movements  of 
the  cross-head,  passed  out  of  reach  or  control  of  the  line  of  string.  The 
pantograph  was  dropped  a  quarter  of  an 
inch  on  the  post,  and  as  much  in  the  cross- 
head,  and  a  long  attempt  was  then  made  to 

repeat  it,  but  it  was  no  use.     Both  indi-  /  I 

cators   were   taken   off  and   carefully   ex-  / 

amined.     Nothing   was   found   out.      The  / 

pantograph  was  again  raised  to  its  original  , ^    ^S 

position,   and    the    matter   was   repeated. 


FIG.  167. 


with  variations,  to  satisfy  us  that  this  kind  of  an  expansion  line  can 
be  produced  by  snapping  the  indicator  string  by  the  movement  of  a 
nail,  peg,  or  any  other  obstruction,  across  the  line  of  the  string.  This  same 
matter  comes  up  wherever  the  pendulum  is  applied  to  any  engine  for  the 
purpose  of  taking  an  indicator  diagram.  In  this  particular  case  the  speed 
of  the  paper  barrel  was  generally  changed,  first  fast  and  then  slow.  The 
same  thing  occurs,  although  it  is  seen  in  a  different  way,  and  will  be  treated 
of  hereafter,  whenever  the  pendulum  motion  is  being  used,  unless  the 
sliding  bar  is  used  to  communicate  the  motion  to  the  indicator  barrel.  When- 
ever the  pendulum  is  so  attached  that  the  motion  is  coincident  with  that  of 
the  piston,  and  is  also  exactly  equal  both  sides  of  the  center,  very  little  varia- 
tion will  appear ;  but  whenever  the  swing  of  the  peg,  or  even  an  arc  of  a 
circle  is  used  to  communicate  motion,  the  distance  traveled  is  unequal  dis- 
tances on  a  straight  line,  while  the  speed  of  the  motion  may  be  uniform ;  the 
travel  being  upon  an  arc  of  a  circle,  it  will  give  an  unequal  distance  when 
applied  to  the  travel  upon  the  slides  by  the  cross-head,  and  this  varies  the 
speed  of  the  indicator  barrel ;  and  while  it  may  be  small  in  amount,  it  is  suf- 


248 


TWENTY  YEARS  WITH  THE  INDICATOR. 


ficient  to  make  the  expansion  line  entirely  unreliable.  This  same  point  can 
be  accomplished  by  boring  a  hole  and  putting  a  little  peg,  which  has  been 
slightly  slotted  on  the  top,  with  partly  rounded  sides,  into  the  peg  arm  of 
the  pantograph  ;  but  if  the  experiment  is  tried,  be  careful  that  this  peg  no 
more  than  strikes  about  one-third  or  one-half  the  diameter  of  the  indicator 
cord,  or  a  paper  barrel  spring  completely  smashed  may  be  the  result.  This 
is  an  extremely  insignificant  point  in  some  respects,  it  is  the  key  to  any  mo- 
tion that  varies,  or  attempts  to  make  straight  travel  by  passing  through  an 
arc  of  a  circle. 

A  CURIOSITY. 

Fig.  168  is  another  experiment  in  steam  engine  building,  scale  30.     This 
was  an  engine  used  in  grinding  rubber.     The  cylinder  was  built  with  Corliss 

valves,  while  a  different  style  regulator 
had  been  attached  to  an  old  bed,  or 
the  girder  part  of  the  bed.  The  several 
diagrams  are  only  a  small  portion  of 
the  erratic  movements  caused  by  the 
changes  in  the  regulator.  The  changes 
in  the  load  were  considerable,  and  the 
regulator  would  sometimes  change  from 
its  highest  to  its  lowest  point  on  the 
very  same  stroke.  Very  little  more  can 
be  said  about  this  figure  than  that  it 
shows  a  regulator  utterly  unfit  to  be 
used  where  any  change  of  load  should 
occur,  and  shows  also  that  there  is  an 
exceedingly  good  opportunity  for  the 
engine  to  smash  itself,  in  case  of  a 
sudden  change  from  one  load  to  the 
other,  that  was  from  the  heaviest  load 
to  the  lightest.  On  the  other  hand,  if 
it  was  suddenly  from  light  to  heavy 
the  engine  would  be  exceedingly  apt 
to  stop.  A,  A,  indicate  the  extreme 
ends  of  the  atmospheric  line  of  the 
instrument,  and,  in  order  to  show  the 
differences  between  the  exhaust  lines 
of  the  different  diagrams,  the  atmos- 

^ — '  .{  pheric    line   is   omitted.     B,    C   and  D 

show  variations,  the  card  intending  to 
''  ''//          cover  ten  strokes  of  the  engine,  speed 
s      •  1 ,  80  per  minute.     It  shows  also  that  the 

^  /  /  Ft 

^^~^'     ''^''/  \  engine  is  entirely  insufficient  in  its  port 

^--j-    ^ '_ >   \  ways  to  exhaust  under  carrying  steam 

FIG.  168.  two-thirds  of  the  stroke.      It  shows  in 


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TWENTY  YEAES  WITH  THE  INDICATOR.  249 

every  case  that  the  valves  are  a  trifle  late  in  their  action,  and  the  steam 
lines  do  not  approximate  very  closely  to  a  Corliss  engine  built  by  any  of  the 
builders  who  understand  their  business.  In  this  case  we  have  a  pretty 
good  cylinder  with  a  very  poor  regulator,  and  an  exceedingly  poor  show- 
ing of  a  Corliss  engine  for  regulation,  but  it  is  a  Corliss  engine  only 
in  name,  like  many  others,  the  improvements  upon  it.  make  it  practically 
worthless,  or  a  departure  from  the  real  Corliss  engine  principles  makes 
a  departure  from  good  practice  and  also  from  good  results.  These  four 
diagrams  cover  an  amount  of  information  which  will  only  be  measured 
by  the  patience  that  the  persevering  reader  shall  give  to  them,  and  the 
benefits  which  he  will  derive  will  only  be  measured  by  his  acuteness  and 
careful  attention,  and  if  these  are  given  many  engineers  will  be  saved  trouble 
or  being  humbugged  by  any  attempt  by  parties  who  are  interested  in  the 
sale  or  attempted  misrepresentation  of  the  actual  working  of  machines. 
Excepting  167,  these  should  all  find  their  way  to  the  scrap-pile,  and  cease  to 
be  an  annoyance  to  the  engineer  in  charge,  as  well  as  to  the  men  who  supply 
steam  and  fuel  for  their  running. 


LESSON  LXXXIII. 


FOR  THE  BEGINNERS. 

During  the  four  years  which  have  elapsed  since  the  first  systematic 
course  of  articles  upon  the  indicator  first  appeared,  the  author  has  found 
very  frequent  inquiries  for  the  elements,  as  men  were  continually  taking  up 
the  indicator  to  learn  something  of  it,  who  had  not  seen  the  first  series  of 
articles,  and  consequently  had  omitted  many  little  points  which  are  essential 
to  men  who  have  never  held  or  handled  the  indicator  ;  to  such  ones  this  les- 
son is  especially  adapted,  while  it  will  not  do  the  older  ones  any  harm  to  oc- 
casionally run  over  it  in  order  to  obtain  other  or  more  information  and  fre- 
quent reference  to  something  about  which  they  may  have  doubts.  The  indi- 
cator is  intended  not  only  to  measure  correctly  the  proper  power  exerted,  but 
it  also  gives  us,  if  correctly  applied,  the  manner  in  which  the  valves  handle 
the  steam ;  it  tells  us  of  the  position  of  the  valves  with  regard  to  the  stroke, 
whether  the  motion  of  the  valves  is  sufficient  or  not.  It  also  tells  us  whether 
the  ports,  passages,  throttle  valves,  steam  pipes,  exhaust  pipes  and  ways  are 
all  sufficient,  or,  if  insufficient.  It  is  not  able  to  tell  the  particular  point  at 
which  the  trouble  is,  but  it  will  give  the  trouble,  and  then  we  must  find 


250 


TWENTY  YEARS  WITH  THE  INDICATOR. 


its  exact  location.  It  frequently  shows  us  that  feed-water  heaters  are  an 
element  of  trouble  by  the  insufficiency  of  the  area  of  the  steain  passage 
allowed  for  the  exhaust  steam.  Sometimes  it  will  tell  us  of  a  leak  in 
valves,  or  of  many  little  points  which  are  not  necessarily  to  be  particular- 
ized here,  so  that  to  cut  the  enumeration  of  all  these  things  short,  the 
indicator  will  tell  us  at  any  time,  if  honestly  applied,  when  the  engine  is 
working  correctly  or  incorrectly ;  if  incorrectly,  it  will  showT  whether  there  is 
back  pressure,  too  late  release,  too  tardy  admission,  throttling  between 
admission  and  expansion,  whether  the  engine  is  overloaded,  or  any  of  these 
numerous  happenings  which  can  be  found  in  item  and  detail  by  the  previous 
lessons  in  this  book.  Directions  have  already  been  given  for  computing ;  any 
one  can  do  this,  who  chooses  to  give  a  little  time  to  it. 

Now  the  standard  in  all  cases  is  the  ideal  or  perfect   diagram.     The 
perfect  steam  engine  (which  has  not  yet  been  built)  is  expected  to  economize 


G    \ 

^ 


FIG.  169. 

by  the  use  of  full  boiler  pressure,  to  cut  it  off  sharply,  expand  it  theoreti- 
cally, release  it  early,  exhaust,  if  non-condensing,  at  the  atmospheric  line,  and 
if  a  condensing  engine,  we  are  expected  to  accomplish  about  14  pounds  of 
vacuum  (theoretically  14.7  at  the  level  of  the  sea)  to  compress  slightly 
according  to  the  fancy  of  the  builder  or  the  engineer,  and  in  this  way  to 
realize  all  the  heat  units  and  the  effective  pressure  upon  the  piston,  and  in 
that  way  make  the  coal  consumption  reduced  to  the  minimum.  The  steam 
engine  cannot,  however,  go  back  to  the  steam  boiler  and  rearrange  inefficient 
furnaces,  too  large  or  too  small  steam  space,  or  any  of  the  thousand  things 
which  may  go  towards  making  an  incomplete,  insufficient,  or  badly  arranged 
boiler  plant.  The  engine  is  expected  to  take  the  steam  pressure  in  the  pipe 
and  use  it  in  the  most  economical  way  ;  for  that  reason,  we  have  constructed 
in  Fig.  169  the  generally-accepted  theoretical  diagram.  It  is  made  upon  a 


TWENTY  YEARS  WITH  THE  INDICATOR.  251 

/scale  of  30  to  the  inch,  having  60  pounds  steam  pressure  and  14.7  pounds  or 
absolute  vacuum.  The  various  lines  to  which  frequent  references  have  been 
made  in  this  book,  are  as  follows  :  A  is  the  absolute  vacuum,  which  differs 
with  the  barometric  reading,  and  we  have  laid  out  the  vacuum  for  the  level  of 
the  sea ;  B  is  the  atmospheric  line  of  the  instrument  or  the  line  at  which  the 
pencil  point  of  the  indicator  rests  after  having  been  thoroughly  heated,  after 
allowing  the  steam  to  come  in  contact  with  the  piston  and  working  parts  of 
the  instrument,  and  then  shut  off  all  steam  connections.  And  here  it  is  well 
to  take  notice  of  a  little  point  which  may  have  been  omitted ;  when  the  indi- 
cator has  been  attached,  the  motion  arranged  and  the  cord  or  wire  connected, 
turn  the  steam  gently  upon  the  spring,  heat  the  instrument  thoroughly,  and 
not  until  this  has  been  done,  should  the  atmospheric  line  be  taken ;  having 
done  this,  now  be  extremely  careful  never  to  allow -a  particle  of  steam  to 
escape  from  the  three-way  cock  while  taking  the  atmospheric  line,  for  if  you  do, 
you  will  distort  the  line,  making  it  too  high  or  too  low  ;  D  represents  the 
boiler  pressure,  and  is  dotted  from  the  point  of  cut-off  E,  I,  the  rest  of  the 
length  of  the  diagram  ;  E  represents  what  is  usually  spoken  of  as  the  steam 
line,  or  that  portion  of  the  diagram  made  between  the  time  the  valve  is 
opened  and  that  portion  of  the  piston  travel  that  the  valve  is  held  open ;  the 
dotted  ordinate,  I,  dropped  from  E  shows  the  point  at  which  the  cut-off  valve 
is  supposed  to  have  positively  closed,  and  C  represents  the  expansion  line  from 
the  point  of  cut-off  E  I  to  the  point  of  release  G'.  We  will  digress  for  a  mo- 
ment. Such  a  steam  line  as  we  have  drawn  in  Fig.  169,  E,  will  not  be  found 
one  time  in  thousands,  the  reason  for  it  is  assignable  to  a  great  variety  of 
causes,  which  may  be  changed  materially  by  either  of  the  following  ;  by  inat- 
tention to  the  correctness  of  the  reducing  motion,  and  insufficient  steam  ports, 
steam  passages  or  steam  pipes,  or  too  small  a  throttle  valve,  to  an  ill-propor- 
tioned travel  of  the  valve  with  reference  to  the  piston ;  wherever  any  of  these 
reasons  operate,  this  line  will  be  modified  in  any  of  a. great  many  ways  which 
are  shown  in  the  preceding  lessons,  as  well  as  in  Figs.  170,  171.  The  expan- 
sion line  C  partakes  of  a  great  many  variations.  It  is  exceedingly  rare  that 
we  find  one  that  approximates  very  closely,  and  for  this  there  are  a  great  many 
different  reasons  ;  the  distortion  of  the  motion,  any  error  in  the  travel  or 
capacity  of  the  valves,  any  leak  in  the  valves,  which  may  be  very  trifling,  will 
make  a  difference  in  this  line.  Leaking  by  the  piston,  the  presence  of  water, 
to  which  is  added  the  variable  speed  of  the  piston,  or  expansion,  diminution 
of  pressure,  increase  in  volume,  a  change  in  the  physical  properties  of  the 
steam,  and  if  the  indicator  itself  be  not  in  perfect  working  order,  the  expan- 
sion line  is  likely  to  be  an  erratic  one.  The  theory  upon  which  the  expansion 
line  is  based  is  that  of  Mariotte's  law,  that  increasing  the  volume  diminishes 
the  pressure  in  a  certain  known  ratio.  This  from  the  very  nature  of  the 
thing,  has  never  been  definitely  proved,  but  the  general  foundation  of  the 
law  is  that  as  the  volume  doubles  the  pressure  decreases  one-half,  and  so  in 
proportion.  At  G'  the  continuation  of  the  dotted,  like  the  expansion  line  C, 
has  been  drawn  at  an  angle  rather  sharper,  perhaps,  than  the  general  con- 
struction of  engines  will  admit  of  in  release,  by  the  actual  lines  of  the  indi- 


252  TWENTY  YEARS  WITH  THE  INDICATOR. 

cator,  but  we  have  drawn  it  thus  distinct,  for  the  working  engineer  has  fre- 
quently an  idea  that  he  should  not  release  until  he  had  obtained  everything 
that  was  possible  out  of  the  steam.  Here  is  a  point  of  practice  about 
which  some  engineers  now  differ,  but  those  with  the  largest  machinery  and 
the  broadest  practice,  have  no  doubt  and  no  difference,  viz.,  if  we  commence 
our  release  at  G',  following  the  line  which  shows  a  rounding  into  the  con- 
denser at  the  extreme  end  of  the  stroke  by  a  full  open  valve,  we  shall  then 
continue  the  line  G  below  the  atmospheric  line,  so  that  it  reaches  the  full 
extent  of  the  vacuum  at  about  one-tenth  of  the  stroke  ;  and  if  the  exhaust 
valve  of  an  engine — taking  the  Corliss  as  standard,  or  any  other  well-con- 
structed engine — opens  a  little  before  the  end  of  the  stroke  in  order  to 
release  the  expanded  steam  as  soon  as  possible,  and  allow  the  condenser  to 
have  full  swing  at  it,  we  shall  close  that  valve  as  much  before  the  end  of  the 
stroke  on  its  exhaust  as  we  open  it  before  the  end  of  the  stroke,  provided  the 
builder  of  the  engine  has  properly  proportioned  the  travel  of  the  valve.  As 
we  are  working  on  an  ideal  card,  we  shall  suppose  we  are  dealing  with  a  first- 


— B~ 

FIG.  170. 

class  builder  so  that  the  distance  from  G'  to  the  end  of  the  stroke,  will  give 
the  condenser  a  wide  open  valve  at  the  very  commencement  of  the  return 
stroke,  and  will  immediately  reduce  the  steam  to  full  vacuum  at  the  intersec- 
tion of  the  lines  G  A  from  the  terminal  pressure  end  of  the  diagram,  and  will 
make  the  dotted  compression  line  G,  touching  the  vertical  line  J  at  about  17 
pounds  above  atmospheric  pressure.  There  is  a  great  difference  of  opinion 
among  engineers,  some  claiming  that  it  is  impossible  to  compress  upon  a  con- 
densing engine.  This  is  a  mistaken  idea,  and,  while  many  prefer  to  run 
their  engines  without  any  compression,  they  will  find,  if  the  engine  is  prop- 
erly constructed,  that  compression  within  a  reasonable  limit  is  invariably  an 
advantage,  because,  if  we  take  the  line  G  as  an  instance,  we  have  17  pounds 
above  the  atmospheric  line  of  pressure  at  the  very  end  of  the  stroke  ;  if, 
now,  the  steam  valve  is  properly  set,  so  that  it  commences  to  open  and 
continues  the  dotted  line  G,  from  its  intersection  with  J,  following  up  the 
line  J,  by  what  is  known  as  the  admission  line,  we  shall  then  have  17 
pounds  pressure  in  that  end  of  the  cylinder  upon  which  we  put  enough 


TWENTY  YEARS  WITH  THE  INDICATOR.  253 

to  bring  it  up  to  60  pounds,  while,  if  we  do  not  have  any  compression, 
we  have  to  put  60  pounds  instead  of  43.  We  have  now  completed 
the  circuit  of  the  diagram  ;  upon  the  same  diagram,  169,  notice  the 
irregularly  dotted  line  H  (which  is  the  most  usual  line  of  compression)  in 
which  the  steam  is  carried  beyond  the  point  G',  by  means  of  the  dotted 
line  H,  which  is  differently  dotted  from  G',  and  where  the  steam  pressure 
is  confined  until  almost  the  extreme  range  of  travel  of  the  piston, 
barely  commencing  to  open  at  the  very  end  of  the  stroke,  in  which  case  the 
irregular  line  H  is  continued  and  shows  the  effect  of  a  later  opening,  so 
that  the  absolute  vacuum  is  not  obtained  until  the  piston  has  traveled 
twice  as  far  on  its  return  stroke,  or  about  one-fifth  of  the  whole  stroke,  as  it 
did  with  the  earlier  release  at  G'.  As  the  motion  of  the  valve  here  is  later, 
so  it  will  be  later  in  closing.  The  line  H  is  supposed  then,  from  the  point 
of  its  intersection  with  A,  to  travel  from  the  line  A  until  it  reaches  H,  where 
it  will  be  found  to  extend  but  little  above  the  atmospheric  line,  making  only 
a  pressure  of  eight  pounds.  The  general  practice  on  condensing  engines  is 
that  wherever  the  late  opening  and  late  closure  are  practiced,  that  it  is  much 
more  frequently  followed  with  7,  8,  9,  or  10  pounds  of  vacuum  instead  of 
14.7.  The  earlier  the  release  consistent  with  proper  compression,  the  larger 
amount  of  vacuum  is  obtained  from  the  same  amount  of  steam.  The  later 
the  release,  the  later  the  compression,  and  the  less  amount  of  vacuum  is  gen- 
erally obtained,  but  as  all  classes  have  their  ideas,  and  we  take  diagrams  from 
all  descriptions  of  adjustments,  we  have  thought  best  to  introduce  here  for 
the  beginner's  benefit,  the  long  dash  and  dotted  line  F,  which  shows  a  very 
general  idea  of  excessive  steam  lead,  joined  to  a  considerable  compression. 
This  line  may  be  made  either  by  excessive  compression  or  by  a  steam  lead ; 
and  by  steam  lead  we  mean  just  this,  that  the  compression  took  place  from  the 
absolute  vacuum  line  A,  and  the  steam  valve  opened  considerably  before  the 
piston  arrived  at  the  end  of  its  stroke  or  the  dead  center.  This  line  will  be 
frequently  found  upon  modern  constructed  engines  where  an  attempt  at  high 
speed  has  been  made,  but  it  is  not  desirable.  The  difference  between  exces- 
sive compression  or  steam  lead,  and  correct  compression  is  simply  this,  if  the 
valve  is  shut  before  the  exhaust  is  complete,  or  slightly  before  the  piston 
arrives  at  the  end  of  the  stroke,  a  small  amount  of  low  tension  steam  is  com- 
pressed gradually  to  a  higher  pressure,  and  consequently  to  a  higher  temper- 
ature, audit  offers  mechanically  a  "cushion*'  upon  which  the  piston  gradually 
strikes,  and  it  comes  to  a  more  gentle  stop  than  as  if  nothing  were  there, 
when  there  would  be  a  certain  amount  of  strain  upon  the  gibs,  keys  and  con- 
nections, if  the  cushion  were  not  present ;  and  with  the  cushion  an  amount  of 
steam  is  saved,  and  the  wear  and  tear  on  the  connections  of  the  piston  rod, 
cross-head,  connecting-rod,  crank-pin  is  reduced. 

For  any  variation  from  the  ideal  diagram  there  is  always  some  reason, 
and  the  beginner  or  the  man  who  has  had  practice,  should  aim  to  obtain  the 
most  perfect  results  that  are  possible,  and,  in  every  instance,  to  investigate 
every  departure  from  the  theoretical,  unless,  as  in  some  of  the  instances 
given,  the  simple  outline  of  a  card  shows  an  exceedingly  faulty  construction ; 


254  TWENTY  YEARS  WITH  THE  INDICATOR. 

and  it  is  sometimes  well  for  a  person  who  has  not  had  much  experience  to 
study  these  very  faulty  cards  for  his  own  benefit  and  future  reference. 

With  a  view  to  some  contrast  we  have  introduced  Fig.  170,  which  is  from 
a  Corliss  engine,  overloaded  and  throttled,  or  choked  in  the  steam  supply. 
Referring  to  this  figure  (170),  A  represents  the  atmospheric  line  of  the  instru- 
ment, B  absolute  vacuum,  C  steam-boiler  pressure,  D  highest  initial  pressure 
realized,  which  is  only  33  pounds  out  of  38.  The  steam  line  from  D  to  E, 
supposing  E  to  be  the  point  of  cut-off,  shows  8  pounds  less  steam  pressure 
at  the  point  of  cut-off  than  at  initial.  This  is  caused  by  the  feed  pipe  being 
too  small,  and  contrasts  strangely  with  the  ideal  line  E  in  Fig,  169.  The 
point  of  cut-off  at  E,  170,  will  be  seen  to  have  been  rounded  over,  which  is 
caused  by  the  slow  closing  of  the  valve,  and  the  expansion  line  in  this  case 
may  proceed  closely  on  the  theoretical  line,  if  he  can  find  the  exact  point  of 
cut-off.  F  is  the  point  of  release  or  evident  opening  of  the  exhaust  valve,  and 


o) 

/ 1 

/  f 

I/     ! 


FIG.  171. 

G  is  the  commencement  of  the  vacuum,  and  it  will  contrast  very  strongly 
with  the  ideal  line  in  Fig.  169,  as  shown,  and  in  this  case  (170)  the  engine 
runs  back  to  nearly  one-third  stroke  before  the  maximum  amount  of  vacuum 
is  obtained.  At  H  the  compression  commences  and  closes  at  I  above  the 
atmospheric  line ;  while  the  steam  line  from  I  to  D,  Fig.  170,  shows  that  the 
valve  commences  to  open  very  slightly  before  the  piston  arrives  at  the  ex- 
treme end  of  its  stroke. 

In  Fig.  171  we  have  another  type  of  very  frequently-found  trouble  wThich 
is  more  marked  in  this  case  from  the  fact  that  it  is  from  a  Corliss  engine. 
Many  engineers  have  an  idea  that  they  must  invariably  get  an  engine  under 
motion  with  a  partly  closed  throttle  valve.  A  Corliss  engine  that  will  not 
start  with  a  throttle  valve  half  open  or  more,  is  decidedly  out  of  adjustment. 
In  this  case  we  will  not,  however,  discuss  anything  except  those  points  which 
the  learner  most  frequently  desires  to  have  thoroughly  fixed  in  his  mind.  The 


TWENTY  YEARS  WITH  THE  INDICATOR.  255 

coarsely  dotted  diagram,  if  we  start  at  the  point  D,  shows  that  the 
steam  valve  opens  too  late  ;  at  the  top  of  the  line,  directly  under  the  letter  H, 
it  will  be  seen  that  the  steam  line  leans  to  the  left,  or  away  from  the  vertical 
line  F.  The  peculiar  shape  of  the  steam  line,  from  H  down  to  E,  is  caused 
by  the  throttle  valve  being  so  nearly  closed  that  steam  enough  is  not 
furnished  to  keep  the  pressure  up  to  the  line  of  realized  pressure  C  ;  conse- 
quently the  cut-off  valve  is  held  open  for  a  greater  proportion  of  the  stroke 
than  would  be  were  the  throttle  valve  wide  open,  in  which  case  the  pressure 
C  would  only  be  realized.  At  E  we  find  the  visible  point  of  cut-off,  or  near 
enough  for  practical  purposes,  is  21£  pounds  below  the  pressure  at  H,  while 
the  expansion  line  runs  below  the  atmospheric,  making  a  loop.  This  loop  is, 
in  all  cases,  resistance,  and  should  be  so  figured  in  computing  the  diagram 
for  power.  If  we  follow  the  exhaust  line  on  the  return  stroke  of  the  piston, 
we  find  a  square  corner  at  the  terminal  of  the  exhaust,  and  the  steam  line 
commences,  leaving  the  vertical  line  F  more  and  more,  which  shows  that  the 
opening  of  the  valve  is  entirely  too  late.  The  fine  dotted  line  shows  the 
eccentric  rolled  forward  on  the  shaft  to  bring  the  steam  line  from  the  point  D 
up  to  the  vertical  line  F,  or  so  that  the  valve  commences  to  open  and  admit 
the  steam  as  soon  as  the  engine  gets  upon  the  dead  center.  It  is  a  fact,  that 
whenever  the  valve  is  late  in  its  opening,  the  pressure  of  steam  is  invariably 
reduced,  and  the  later  the  valve  is  in  its  opening,  the  greater  the  reduction  of 
realized  pressure.  In  this  case,  after  the  eccentric  has  been  thrown  forward 
to  bring  the  steam  line  proper  up  to  the  vertical  line  F,  which  is  at  right 
angles  to  the  vacuum  A,  and  atmospheric  B,  as  well  as  the  realized  pressure 
in  the  first  case,  C,  it  will  be  seen  that  the  realized  pressure  on  the  piston  in- 
creased nearly  five  pounds,  or  to  the  line  G.  In  this  case  the  throttle  valve  is 
wide  open ;  notice  the  beauty  of  the  expansion  line  J,  which  we  have  only 
drawn  until  it  reaches  the  exhaust  line  at  about  the  point  B.  This  would 
make  decidedly  more  of  a  loop  than  the  coarser  dotted  diagram,  but  in  mov- 
ing the  eccentric  forward  we  have  also  accomplished  another  very  important 
and  economical  point,  which  is  the  compression.  Notice  the  fine  dotted  line 
I,  which  compresses  the  steam  23  pounds  to  the  point  D,  at  which  point  the 
steam  valve  commences  to  open  and  fills  the  cylinder  with  steam  the  balance 
of  the  56  pounds.  Both  these  objects,  viz.,  opening  the  steam  valve  at  the 
proper  time  and  closing  the  exhaust  valve  quicker,  are  accomplished  in  this 
case  by  moving  the  eccentric  about  three-quarters  of  an  inch  of  the  circumfer- 
ence of  the  shaft  forward.  Sometimes  when  this  is  done  we  may  throw  one 
valve  exactly  up  to  the  right  point  and  the  other  one  may  be  too  quick,  or 
to  give  too  early  a  steam  line,  and  it  may  affect  the  exhaust  valve  or  com- 
pression and  release  in  the  same  way.  Get  the  steam  valves  right  by  means 
of  the  jim-crank  connection,  and  on  the  Buckeye  engine,  get  them  right  by 
the  compensation  arrangement  on  the  valve  rod,  by  which  you  can  divide 
the  travel  of  the  valve,  or  any  difference  in  the  travel  to  the  hundredth  of  an 
inch.  In  the  Armington  &  Sims  engine  this  is  usually  done  at  the  shop,  but 
in  case  of  tinkering  or  changes,  take  off  the  valve  chest  cover,  and  move  the 
check-nuts  on  either  end  of  the  valve  until  you  have  it  exactly  where  you 


256  TWENTY  YEARS  WITH  THE  INDICATOR, 

want  it,  and  whenever  any  changes  on  the  engine  are  made  in  this  way,  pay 
no  attention  to  prick-punch  marks,  cold-chisel  slashes,  or  anything  of  that 
sort,  work  by  the  lines  of  the  indicator,  taking  care  that  they  are  perfectly 
correct  in  their  motion,  corresponding  to  an  absolute  reduction  from  the 
travel  of  the  piston.  In  this  way  no  difficulty  will  be  found  in  adjusting 
the  valves  of  a  Corliss  engine  to  an  exactness  that  will  give  a  small  fraction 
of  a  horse-power  difference  on  a  large  engine  between  the  ends. 

On  some  of  the  slide-valve  engines,  it  is  exceedingly  difficult  to  balance, 
for  we  frequently  find  the  travel  of  the  valve  not  correctly  calculated,  in 
which  case  we  must  work  for  the  best  good  of  most  of  the  factors  in  the 
combination.  Sometimes  we  have  to  sacrifice  a  little  on  the  steam  line  for 
the  sake  of  being  sure  of  a  good  release,  and  at  other  times  we  get  a  release 
without  compression  for  the  sake  of  admitting  the  greatest  amount  of 
pressure. 

But  there  are  other  methods  of  attaching  the  indicator  which  are  very 
valuable.  Fig.  172  shows  two  different  diagrams  taken  at  different  times, 

*_.  A-=      -----       -4 


C 

FIG.  172. 

but  both  for  the  same  purpose.  These  are  what  are  termed  steam-chest  or 
steam-pipe  diagrams  ;  they  are  taken  by  attaching  the  steam  engine  indi- 
cator to  the  steam  chest  where  possible,  or  to  the  steam  pipe  below  the 
throttle  Valve,  and  connecting  the  indicator  with  the  same  motion  by  a 
separate  cord  (taking  pains  that  no  angles  except  right-angles  are  made) 
with  which  the  indicators  at  the  end  of  the  cylinder  are  driven.  Care  should 
be  taken  to  make  the  steam  pipe  diagram  of  the  same  length,  as  nearly  as 
possible,  with  the  diagram  from  each  end  of  the  cylinder.  In  that  case  the 
proportions  between  them  are  precise,  while  in  the  case  of  a  longer  or  shorter 
one  it  requires  figuring  to  learn  their  proportions. 

Fig.  A,  172,  was  taken  in  1868  from  a  Harris-Corliss  engine,  scale  30,  to 
ascertain  what  proportion  of  boiler  pressure  was  realized,  and  a  little  study 
of  the  diagram  will  satisfy  any  engineer  that  these  steam-pipe  or  steam-chest 
diagrams  are  quite  as  valuable  as  those  taken  from  the  end  of  the  steam  cyl- 
inder, and  frequently  they  give  us  a  clue  to  what  occurs  before  the  steam 


TWENTY  YEARS  WITH  THE  INDICATOR.  257 

reaches  the  steam  chest,  so  that  we  may  not  pull  the  engine  down  but  rather 
pull  down  the  pipe  and  go  back  to  find  the  trouble.  If  we  start  at  figure  1 
and  follow  the  line  in  the  direction  of  the  arrow  to  2,  we  find  that  the  press- 
ure in  the  steam  chest  is  slowly  diminished,  while  the  valve  at  that  end  of 
the  cylinder  is  held  open,  and  this  distance  from  1  to  2  shows  the  exact 
distance  that  the  valve  was  held  open,  or  until  it  completely  closes,  in  feeding 
the  cylinder  with  the  amount  of  steam  allowed  by  the  position  of  the  regu- 
lator cams  at  that  instant  of  time.  The  valve  commenced  to  close  at  2  and 
the  pressure  gradually  increased  up  to  3  ;  the  valve  was  at  that  time  fully 
closed  and  the  pressure  ran  along  to  just  beyond  A,  where  the  pressure 
dropped  slightly  by  the  draft  of  steam  in  the  pipe.  At  4  the  other  end  of 
the  valve  opened  and  steam  was  carried  from  4  to  5,  at  which  point  the  valve 
commenced  to  close  and  made  a  more  abrupt  closing  from  5  to  6  than  from  2 
to  3. 

This  diagram  in  itself  is  one  of  the  finest  we  have  ever  taken,  and  if 
carefully  taken,  they  tell  the  action  of  the  steam  in  the  pipe,  precisely  how 
far  steam  is  carried  on  the  cylinder,  when  the  valve  opens  and  when  it  closes, 
and  every  fluctuation  of  pressure  which  occurs  in  the  pipe  from  beginning  to 
end.  Fig.  B,  172,  is  from  a  Buckeye  engine,  at  the  American  Institute  Fair 
in  New  York,  taken  in  November,  1884,  scale  50.  This  engine  was  running 
from  222  to  225  revolutions,  and  it  presents  a  contrast  to  the  other  diagram, 
from  the  fact  that  a  large  amount  of  compression  was  shown  upon  the  right- 
hand  end  and  a  moderate  amount  upon  the  other.  At  figure  1  the  pressure 
falls  with  the  opening  of  the  valve  in  the  steam  pipe,  is  immediately  raised 
by  too  much  compression,  and  this  occurs  while  there  is  but  a  very  slight 
movement  on  the  part  of  the  piston  toward  the  completion  of  its  stroke. 
The  steam  pressure  is  then  led  off  by  the  opening  of  the  valve,  toward  B, 
falling  off  very  little  indeed.  It  will  be  noticed  that  the  curve  on  the  Buck- 
eye engine,  formed  by  the  closure  of  the  valve,  is  somewhat  longer  than 
that  on  the  Harris-Corliss  engine  from  2  to  3.  The  Buckeye  uses  the  slide 
valve,  the  motion  is  slightly  slower,  although  it  is  very  fast.  We  then 
reach  the  highest  limit  of  pressure.  On  the  other  end  of  the  engine,  at 
the  commencement  of  the  stroke,  or  opening,  the  pressure  slightly  dimin- 
ishes, holds  steady  for  the  first  half  of  admission  and  then  the  pressure 
slightly  falls  away,  until  the  time  of  the  closing  of  the  valve.  Both  dia- 
grams are  very  fine  and  show  the  difference  in  practice  between  the  valves ; 
C  in  both  cases  represents  the  atmospheric  line.  When  these  steam-pipe  or 
steam-chest  diagrams  are  of  exactly  the  same  length  as  the  cylinder  dia- 
gram, they  are  exceedingly  useful,  and  they  should  be  taken  from  every 
engine  that  has  indicator  connections  or  attachments. 

Another  good  place  for  the  indicator  to  be  attached  is  to  vlie  exhaust 
pipe  between  the  engine  and  the  heater,  or  between  the  engine  and  con- 
denser. Care  must  be  taken,  however,  in  the  case  of  a  condensing  engine 
whenever  the  indicator  is  to  be  applied,  never  to  turn  the  three-way  cock 
so  as  to  break  the  connection  between  the  condenser  and  steam  engine  cyl- 
inder. In  the  case  of  a  condensing  engine,  we  can  frequently  find  where  a 


*58  TWENTY  YEARS  WITH  THE  INDICATOR. 

part  of  the  difference  between  the  vacuum  gauge  and  realized  vacuum  is 
accounted  for ;  in  the  case  of  a  high-pressure  engine  we  frequently  obtain 
from  this  a  back  pressure  of  from  one-half  to  two  or  three  pounds,  and  in 
cases  where  the  steam  is  returned  or  changed  in  its  direction  through  the 
feed-water  heater,  we  sometimes  find  that  the  heaters  have  not  the  same  area 
in  their  tubes  as  the  exhaust  pipe  has.  All  of  these  things  the  indicator  is 
perfectly  applicable  to,  and  with  proper  connections  will  be  found  of  great 
value,  or  quite  as  much  so  as  in  the  case  of  the  cylinder  itself. 

It  is  also  interesting  to  indicate  steam  pumps  or  water  pumps,  as  we 
sometimes  get  a  very  curious  record  of  the  operations  which  go  on  inside 
a  cylinder,  to  show  us  that  the  pump  throws  wrell  one  way  and  not  well  the 
other ;  and  it  is  often  to  our  advantage  to  examine  these  things,  for  we  may 
find  the  valves  on  one  end  of  the  pump  seriously  out  of  order,  and  in  that 
way  avoid  trouble  in  case  of  fire,  or  when  the  pump  is  called  upon  suddenly 
to  do  its  utmost  work.  In  some  cases  of  steam-pipe  throttling,  it  is  well 
to  have  diagrams  taken  from  different  parts  of  the  pipe  (the  motion  can  be 
readily  transferred  to  almost  any  distance  by  using  carrier  pulleys)  and  in 
this  way  we  frequently  locate  troubles,  where  nothing  but  taking  down  a 
large  steam  drum  or  main  steam  pipe  would  allow  the  object  to  be  accom- 
plished otherwise. 

It  is  well  for  the  beginner  to  also  practice  somewhat  with  different 
motions,  to  ascertain  which  are  correct  and  which  are  incorrect.  Get  the 
length  of  your  travel  on  the  diagram  on  the  paper  cylinder,  then  divide  this 
into  four  equal  parts,  or  into  as  few  or  as  many  parts  as  you  choose,  turn  the 
engine  over  carefully,  and,  if  you  are  using  the  pendulum,  you  will  soon 
find  that  you  cannot  make  a  peg,  traveling  the  arc  of  a  circle,  conform 
to  the  exact  divisions  of  the  travel  of  the  cross-head  on  the  paper  cylinder. 

Another  point,  which  frequently  makes  trouble  for  beginners,  is  the 
deducting  the  piston-rod  area  from  the  effective  area  of  the  cylinder.  The 
crank  end  of  the  engine  has  the  size  of  the  piston  rod  to  be  deducted  from 
the  area  of  the  piston  ;  beginners  sometimes  are  troubled  by  not  knowing 
whether  this  should  be  taken  from  both  ends,  or  from  one  end.  It  can  only 
be  taken  from  the  end  that  it  exists  on.  If  we  have  a  piston  30  inches  in 
diameter,  and  a  piston  rod  3  inches  in  diameter,  we  take  the  area  of  the 
3-inch  piston  rod  from  the  area  of  the  20-inch  piston ;  the  difference  is  insig- 
nificant, but  the  beginner  may  as  well  figure  it  for  a  few  times  and  ascertain 
that  it  is  an  almost  unimportant  factor,  unless  in  the  case  of  steamship 
engines,  where  we  sometimes  have  a  piston  120  inches  in  diameter,  with  a 
trunk  varying  from  36  to  50  inches ;  it  then  becomes  an  element  of  very 
great  importance.  A  great  many  hints  as  they  occurred  in  practice,  will  be 
found  in  the  various  lessons  preceding  this,  and  they  can  only  be  properly 
studied  by  carefully  studying  each  lesson  by  itself,  for  they  are  best  remem- 
bered when  the  circumstances  under  which  they  occurred,  are  recorded. 


TWENTY  TEAMS  WITH  THE  INDICATOR. 


LESSON  LXXXIV. 


WATER  PER  HORSE-POWER  FROM  THE  DIAGRAM,  OR  STEAM  CONSUMED. 

It  is  very  frequently  necessary  to  make  a  computation  either  upon  the 
amount  of  steam  per  horse-power,  or  the  amount  of  water  per  horse-power 
accounted  for  by  the  diagram.  These  matters  are  to  a  certain  extent  com- 
plex ;  not,  however,  from  necessity  or  reality,  but  because  they  have  fre- 
quently been  made  to  appear  complex  by  the  amount  of  figures  incorporated 
into  them.  All  computations,  as  we  have  stated,  must  be  from  the  absolute 
vacuum,  for  on  that  line  is  founded  the  temperature,  volume,  weight  and 
other  properties  of  steam.  The  reader  of  this  volume  will  by  this  time  have 
become  familiar  with  the  reasons  why  this  base  line  is  assumed  in  every  case 
as  the  only  basis  of  actual  comparison.  If  we  wish  to  ascertain  the  amount 
of  steam  consumed  from  the  diagram,  or,  as  it  is  frequently  termed,  steam 
accounted  for  by  the  indicator,  we  take  the  absolute  vacuum  at  14. 7  "below  the 
atmospheric  line  of  the  diagram.  For  real  correctness  the  clearance  of  the 
engine  must  be  known,  and  this  amount,  the  clearance,  should  be  added  to 
the  diagram  on  a  scale  equal  to  the  scale  of  the  diagram.  If  the  diagram  is 
four  inches  long  and  represents  a  stroke  of  four  feet,  five  feet,  ten  feet,  or  twelve 
feet,  it  is  easy  to  ascertain  precisely  what  any  fraction  of  the  four  inches 
represents  proportionately.  Add  to  the  diagram  of  the  indicator  the  clear- 
ance, if  you  can,  and  this  clearance  must  include  the  cubic  inches  between 
the  piston  and  the  cylinder  head  at  full  stroke ;  also,  the  exhaust  port  to 
the  face  of  the  valve,  and  the  steam  port  to  the  face  of  the  valve  as  well. 
It  is  usual  to  figure  the  amount  of  steam  consumed,  or  accounted  for,  from 
the  point  of  release.  This  is  not  necessary,  and  sometimes  it  is  absolutely 
impossible,  to  tell  precisely  where  release  commences.  Take  any  point  on 
the  line,  either  at  the  point  of  cut-off,  or  on  any  point  of  the  expansion  line 
before  the  exhaust  valve  opened.  Now  take  the  length  of  the  stroke,  in- 
cluding the  clearance,  up  to  the  point  where  the  pressure  is  measured,  and 
from  which  point  the  computation  is  to  be  made.  Multiply  the  length  of 
the  stroke  to  that  point  by  the  area  in  square  inches  of  the  cylinder ;  this 
will  give  you  the  volume  of  the  cylinder  to  that  point,  and  to  this  amount 
must  be  added  the  number  of  square  inches  of  clearance  up  to  the  point  of 
the  computation,  this  gives  the  volume  of  the  cylinder ;  multiply  by  the 
pressure  to  the  point  of  computation  ;  divide  this  product  by  14.7 ;  this 
quotient  gives;  the  number  of  cubic  inches  of  steam  at  the  pressure  of  the 
atmosphere  discharged  from  the  cylinder  at  a  single  stroke,  or  to  that  point 
of  the  stroke  where  the  pressure  is  taken.  If  there  is  no  leak  in  the  valves, 
and  the  steam  is  not  saturated  with  water,  the  cubical  contents  of  the  cylin- 


260  TWENTY  YEARS  WITH  THE  INDICATOR. 

der  multiplied  by  the  pressure  at  the  point  of  cut-off  should  exactly  coincide 
with  the  cubic  contents  multiplied  by  the  pressure  at  the  actual  point  of 
release.  If  both  cut-off  and  release  are  well  defined,  it  is  a  good  plan 
always  to  make  both  these  computations,  and  it  will  frequently  be  found 
that  the  point  of  release  gives  the  greatest  amount.  This  at  once  shows  a 
leak.  In  a  compound  engine  the  cubic  contents  of  both  cylinders  should 
agree  with  each  other,  if  the  computation  is  made  in  this  way  from  the  points 
of  release  in  both  cases.  Having  reached  the  cubic  inches  of  steam  at 
the  pressure  of  the  atmosphere,  multiply  this  by  the  number  of  strokes  in  an 
hour,  and  don't  get  confused,  you  are  working  upon  one  side  of  the  piston 
only  ;  take  care  that  revolutions  are  not  considered,  for  in  the  one  case  you 
will  get  double,  and  in  the  other  half  the  actual  result.  Having  multiplied 
by  the  number  of  strokes  in  an  hour,  or  the  number  of  times  that  end  of  the 
cylinder  is  filled  with  steam  in  an  hour  and  exhausted,  divide  this  product  by 
1728,  the  number  of  cubic  inches  in  a  foot,  in  order  to  reduce  cubic  inches  to 
cubic  feet.  We  have  now  the  number  of  cubic  feet  of  steam  used  per  hour, 
divide  this  by  the  indicated  horse-power  of  the  diagram  and  you  have  the 
cubic  feet  of  steam  per  horse-power  per  hour.  If  the  amount  of  water  used 
or  accounted  for  is  required,  divide  the  number  of  cubic  feet  of  steam  per 
hour  by  1700,  this  gives  the  cubic  feet  of  water  used  per  hour.  If  pounds  of 
water  are  wanted,  multiply  the  last  result  by  62^ ;  or,  if  gallons  are  wanted, 
divide  the  product  by  8.33  pounds  for  wine  gallon.  Care  must  be  taken  in 
making  these  computations  to  get  at  the  average  or  actual  power  required.  It 
is  hardly  possible  for  the  indicator  to  account  for  all  the  steam  consumed  or 
all  the  water  used,  for  as  a  matter  of  fact  any  excess  of  leakage,  or  any 
change  of  circumstances,  such  as  blowing- off,  will  require  a  larger  amount  of 
water  in  the  boiler  than  the  indicator  can  account  for ;  the  indicator  simply 
accounts  for  what  is  used  at  and  in  the  engine,  and  the  indicator  cannot  ac- 
count for  leakage  from  any  cause. 

Or,  to  repeat  the  formula  in  a  different  way,  without  the  explanations, 
obtain  the  volume  of  the  cylinder  to  any  point  which  is  perfectly  plain,  be- 
tween the  point  of  cut-off  and  the  point  of  release  ;  this  is  in  cubic  inches, 
and  must  be  multiplied  by  the  pressure  at  the  above  point  from  the  vacuum ; 
then  divide  by  14.7,  the  pressure  of  steam  at  the  atmospheric  pressure,  this 
gives  in  cubic  inches  the  amount  of  steam  discharged  at  each  stroke.  This 
quotient  is  multiplied  by  the  number  of  strokes  or  times  that  the  cylinder  is 
filled  at  one  end  per  hour ;  .this  gives  the  total  number  of  cubic  inches  of 
steam  accounted  for  by  the  number  of  strokes  which  are  made  in  one  hour  ; 
this  is  reduced  to  cubic  feet  by  dividing  by  1728,  which  gives  cubic  feet  of 
steam.  Divided  the  cubic  feet  of  steam  by  1700,  the  volume  of  steam  at 
atmospheric  pressure,  and  the  result  gives  us  cubic  feet  of  water  ;  multiply 
this  last  result  by  62^  and  we  have  pounds  of  water ;  this  divided  by  the 
horse-power  gives  us  pounds  of  water  per  horse-power  for  one  hour. 


TWENTY  YEARS  WITH  THE  INDICATOR.  261 

ANOTHER    METHOD    OF    COMPUTING    THE  WATER    PER    HORSE-POWER 

PER  HOUR. 

The  volume  of  the  cylinder  multiplied  by  the  number  of  strokes  per 
minute,  multiplied  by  60,  or  the  minutes  per  hour,  divided  by  1728,  gives 
cubic  feet.  Multiply  the  last  result  by  the  weight  of  a  cubic  foot  of  steam  at 
the  pressure  at  the  point  of  cut-off — or  the  point  from  which  the  computation 
is  made,  using  the  pressure  above  absolute  vacuum — and  divide  this  last  by 
the  horse-power,  and  the  final  result  will  be  pounds  of  water  per  horse-power 
per  hour.  (See  table  of  "Properties  of  Saturated  Steam"  for  weight  of  one 
cubic  foot  in  decimals  of  a  pound.) 


VACUUM. 


TEMPERATURE    AT   DIFFERENT    ''POUNDS    PER    SQUARE    INCH"    AND 

"  INCHES  OF  MERCURY." 

The  very  peculiar  position  in  which  we  are  placed  in  using  one  or  the 
other  of  the  thermometer  scales,  now  generally  in  use  or  cited  by  scientific 
men  in  experiments,  or  in  contrast  or  comparison  of  results,  makes  an 
enormous  amount  of  trouble  and  bungling  by  comparing  all  others  with 
the  Fahrenheit  scale  which  commences  on  an  assumption  over  300°  from 
correct  and  ends  in  a  guess,  or,  as  Mr.  Porter  has  so  aptly  said,  "  begins  in  a 
blunder  and  ends  nowhere." 

Fahrenheit  assumes  32°  as  freezing,  and  212°  as  boiling.  Centigrade 
gives  0°  as  corresponding  to  freezing  on  the  F.  scale,  and  100°  on  his  ther- 
mometer to  boiling,  or  212°  on  the  F.  The  general  adoption  of  the  Centi- 
grade scale  for  scientific  purposes,  ai  home  and  abroad,  should  be  much  more 
general,  as  the  F.  does  not  commence  with  fact  or  continue  with  accuracy. 

TOTAL  HEAT. 

There  is  no  term  used  which  is  more  of  a  misnomer.  Absolute  cold  has 
been  determined  with  all  reasonable  certainty  as  459°  to  461°  below  the  arbi- 
trary point  as  assumed  by  Fahrenheit,  so  that  in  the  tables  of  all  scientific 
works  •'  total  heat "  is  a  false  application  of  a  term,  notably  in  some  of  the 
literature  which  has  emanated  from  the  United  States  Bureau  of  Steam 
Engineering,  and  total  heat  expresses  only  from  Fahrenheit's  assumed  zero. 


262  TWENTY  YEARS  WITH  THE  INDICATOR. 

INCHES  OF  MERCURY. 

Usage  has  confirmed  the  use  of  a  scale  as  rude  as  the  tally  stick  of 
ball  players  in  our  younger  days,  when  notches  were  cut  in  a  stick  with  no 
graduation  or  calculation,  simply  guessed  at.  The  English  government  have 
adopted  at  the  Koyal  Arsenal  at  Woolwich,  mercurial  gauges  based  on 
equal  divisions  from  the  "  standard  of  usage,"  that  15  pounds  to  the  square 
inch  equals  30  inches  of  mercury,  and  the  curious  feature  of  these  "standard" 
gauges  to  us,  on  examination,  was  the  fact  that  each  pound  pressure  coincided 
with  even  inches. 

The  expansion  of  mercury  for  each  increase  in  its  temperature  of  one 
degree  F.  equals  .000100854  inch. 

The  starting  point  is,  mercury  at  32°  F.  equals  a  volume  of  1,  and  as  the 
changes  in  temperature  occur — if  mercury  is  to  measure  the  changes — then  we 
must  correct  the  column  of  mercury  for  the  degrees.  Hence  it  follows  that 
inches  of  mercury  do  not  follow  any  assumed  or  empirical  scale  of  equal 
inches,  and  when  so  combined  neither  element  shows  a  correct  reading. 

One  pound  pressure  in  inches  of  mercury  equals  2.03601  inches. 

The  specific  gravity  of  mercury  is  13.595  +  . 

Water  is  at  its  greatest  density  at  39^2°  F.  or  4°  C.,  and  M.  Regnault  has 
brought  out  some  curious  facts  in  his  elaborate  experiments  on  air,  water 
and  steam  ;  and  these  are  so  extensive  and  so  valuable  that  all  persons  who 
study  steam  should  have  them  at  hand. 

He  has  determined  that  saturated  steam  cannot  be  investigated  separately 
on  account  of  "  the  expansion  and  contraction  of  its  volume  consequent  on 
changes  of  pressure,  and  those  consequent  on  temperature,  because  at  the 
same  time  its  volume  is  being  contracted  under  increasing  pressure,  its 
expansion  takes  place  with  increasing  temperature,"  so  that  the  density  of 
saturated  steam  is  an  unsolved  problem,  and  Mariotte  gives  us  data  approach- 
ing exactness  from  formulae  of  air,  which,  under  a  constant  pressure  doubles 
its  volume  on  an  increase  of  temperature  of  272.8°  C.,  or  491°  F.,  and  in  tem- 
perature of  steam  a  confusion  exists  at  the  same  pressure  by  different  au- 
thorities, and  frequently  some  unexplained  feature  exists  which  may  be  the 
point  from  which  they  start  out,  and  we  have  to  ascertain  this  point  and  add 
or  subtract  32°,  or  some  other  number,  frequently,  in  order  to  reconcile  the 
data  given. 

THE  DENSITY  OF  STEAM  is  1,  divided  by  the  volume  at  any  given  pressure, 
and  at  the  atmospheric  pressure  the  volume  is  1702,  so  that  the  density  be- 
comes the  fraction  17*02  that  of  water  at  same  pressure. 

TEMPERATURE  OF  VACUUM. 

The  following  table  is  from  M.  Regnault  by  transposition,  and  shows 
the  pounds  per  square  inch.  The  temperature  and  the  inches  of  mercury 
corrected  for  temperature.  The  temperature  is  given  by  each  4°  F.,  and  the 


TWENTY  YEARS  WITH  THE  INDICATOR. 


263 


fractions  are  closely  as  possible  expressed  in  three  places  in  the  first  column, 
and  four  places  in  the  third  column. 

The  unit  of  heat  being  the  heat  required  to  raise  the  temperature  of  one 
pound  of  water  1°  F.,  if  we  require  to  compute  from  any  point ;  the  heat  con- 
tained in  the  water  from  the  starting  point,  32°  F.,  must  be  subtracted  from 
the  heat  given,  and  we  can  then  convert  into  steam  from  and  to  any  pressure, 
from  any  of  the  tables  in  this  work  : 


Pounds  per 
square  inch. 

Temperature. 

Inches  of 
Mercury. 

1.127 

208° 

2.3028 

2.186 

204 

4.4538 

3.172 

200 

6.4638 

4.095 

196 

8.3428 

4.954 

192 

10.0948 

5.755 

188 

11.7258 

6.497 

184 

13.2418 

7.190 

180 

14.6508 

7.833 

176 

15.9588 

8.427 

172 

17.1718 

8.978 

168 

18.2948 

9.489 

164 

19.3338 

9.959 

160 

20.2928 

10.393 

156 

21.1768 

10.792 

152 

21.9928 

11.162 

148 

22.7428 

11.499 

144 

23.4318 

11.811 

140 

24.0638 

12.093 

136 

24.6418 

12.352 

132 

25.1718 

12.591 

128 

25.6548 

12.807 

124 

26.0958 

13.004 

120 

26.4968 

Pounds  per 
square  inch. 

13.182 
13.345 
13.493 
13.624 
13.743 
13.852 
13.948 
14.035 
14.114 
14.183 
14.245 
14.300 
14.350 
14.393 
14.431 
14.465 
14.495 
14.521 
14.543 
14.563 
14.581 
14.596 


Temperature. 

116° 

112 

108 

104 

100 

96 

92 

88 

84 

80 

76 

72 

68 

64 

60 

56 

52 

48 

44 

40 

36 

32 


Inches  of 
Mercury. 

26.8608 
27.1908 
27.4908 
27.7588 
28.0038 
28.2238 
28.4218 
28.5988 
28.7588 
28.8988 
29.0249 
29.1374 
29.2372 
29.3256 
29.4038 
29.4726 
29.5335 
29.5867 
29.6334 
29.6742 
29.7097 
29.7407 


As  32°  F.  is  the  freezing  point  we  stop  at  that  point,  as  there  would  be 
no  economy  in  going  to  that  point,  even  if  it  were  a  possibility.  The  point 
of  greatest  economy  by  marine  engineers  is  now  considered  to  be  about  124° 
F.,  at  which  point  the  changes  of  temperature  are  not  so  radical  as  with  more 
vacuum,  and  a  greater  degree  of  cold  in  its  action  on  the  surfaces  of  piston 
and  cylinder. 

We  believe  in  a  less  vacuum  as  a  means  of  greater  economy  ;  and  that 
some  of  the  examples  of  compounding,  as  shown  in  this  work,  are  but  an 
approach  to  the  highest  economy  in  the  application  of  steam  to  motive 
power. 


264  TWENTY  YEAH.S  WITH  THE  INDICATOR. 


HEIGHT    OF   WATER    COLUMN    DUE    TO    UNBALANCED    PRESSURE    IN 
CHIMNEY  ONE  HUNDRED   FEET  HIGH. 


Temperatni 
in  the 
Chimney. 

•e 

Temperature  of  the  External  Air  —  Barometer,  14.7. 

0° 

10° 

20° 

30° 

40° 

50° 

60 

70° 

80° 

90° 

1OO° 

200 

.453" 

.419 

.384 

.353 

.321 

.292 

.263 

.234 

.209 

.182 

.157 

210 

.470 

.436 

.401 

.371 

.338 

.339 

.280 

.251 

.227 

.200 

.175 

220 

.488 

.453 

.419 

.388 

.355 

.326 

.2°8 

.269 

.244 

.217 

.192 

230 

.505 

.470 

.436 

.405 

.372 

.344 

.315 

.286 

.261 

.234 

.209 

240 

.520 

.488 

.451 

.421 

.388 

.359 

.330 

.301 

.276 

.250 

.225 

250 

.537 

.503 

.468 

.438 

.405 

.376 

.347 

.319 

.294 

.267 

.242 

260 

.555 

.528 

.484 

.453 

.420 

.392 

.363 

.334 

.309 

.282 

.257 

270 

.568 

.534 

.499 

.468 

.436 

.407 

.378 

.349 

.324 

.298 

.273 

280 

.584 

.549 

.515 

.482 

.451 

.422 

.394 

.365 

.340 

.313 

.288 

290 

.597 

.563 

.528 

.497 

.465 

.436 

.407 

.379 

.353 

.326 

.301 

300 

.611 

.576 

.541 

.511 

.478 

.449 

.420 

.392 

.367 

.340 

.315 

310 

.624 

.589 

.555 

.524 

.492 

.463 

.434 

.405 

.380 

.353 

.328 

320 

.637 

.603 

.568 

.538 

.505 

.476 

.447 

.419 

.394 

.367 

.342 

830 

.651 

.616 

.582 

.551 

.518 

.489 

.461 

.432 

.407 

.380 

.355 

340 

.662 

.638 

.593 

.563 

.530 

.501 

.472 

.443 

.410 

.392 

.367 

350 

.676 

.641 

.607 

.576 

.543 

.514 

.486 

.457 

.432 

.405 

.380 

360 

.687 

.653 

.618 

.588 

.555 

.526 

.497 

.468 

.444 

.417 

.392 

370 

.699 

.664 

.630 

.599 

.565 

.538 

.509 

.480 

.455 

.428 

.403 

380 

.710 

.676 

.641 

.611 

.578 

.549 

.520 

.492 

.467 

.440 

.415 

390 

.722 

.687 

.652 

.622 

.589 

.561 

.532 

.503 

.478 

.451 

.426 

400 

.732 

.697 

.662 

.632 

.598 

.570 

.541 

.513 

.488 

.461 

.436 

410 

.743 

.708 

.674 

.643 

.610 

.583 

.553 

.524 

.499 

.472 

.447 

420 

.753 

.718 

.684 

.653 

.620 

.591 

.563 

.534 

.509 

.482 

.457 

430 

.764 

.730 

.695 

.664 

.632 

.602 

.574 

.545 

.520 

.493 

.468 

440 

.774 

.739 

.705 

.674 

.641 

.612 

.584 

.555 

.530 

.503 

.478 

450 

.783 

.749 

.714 

.684 

.651 

.622 

.593 

.564 

.540 

.513 

.488 

460 

.793 

.758 

.724 

.694 

.660 

.632 

.603 

.574 

.549 

.522 

.497 

470 

.802 

.768 

.733 

.703 

.670 

.641 

.612 

-584 

.559 

.532 

.507 

480 

.810 

.776 

.741 

.710 

.678 

.649 

.620 

.591 

.566 

.540 

.515 

490 

.820 

.785 

.751 

.720 

.687 

.659 

.630 

.601 

.576 

.549 

.524 

600 

.829 

.791 

.760 

.730 

.697 

.669 

.639 

.610 

.586 

.559 

.534 

TWENTY  YEAKS  WITH  THE  INDICATOR 


HOW  TO  TEST  FEED  WATEE  FOK  BOILERS. 


Feed-water  heaters  are  a  matter  of  great  importance  ;  they  are  not 
always  put  in  as  they  should  be,  nor  are  they  given  credit  for  all  that  they 
cto,  or  even  all  that  they  are  capable  of,  and  in  a  great  many  cases  they  are 
nor  used,  as  they  might  be,  for  the  profit  or  benefit  of  the  owner.  Testing 
the  temperature  of  feed  water  for  a  boiler,  is  not  an  agreeable  or  desirable 
undertaking  at  all  times,  but  it  is  a  matter  which  can  be  done  every  hour  in 
the  day,  if  the  engineer  in  charge  will  only  think  so.  It  is  a  matter  not  gen- 
erally understood,  that  the  feed  water  varies  a  great  deal  whether  it  is  tested 
under  pressure  or  in  the  open  air.  Water  cannot  and  will  not  show  any 
temperature  greater  than  212°,  if,  indeed,  it  does  that,  unless  it  is  under 
pressure.  It  is  remarkable  that  engineers  will  insist  in  drawing  water  out  of 
a  boiler  under  60  or  80  pounds  pressure,  and  dip  a  thermometer  in  the  cur- 
rent of  water  which  is  running  away  from  the  boiler  into  the  open  air,  and 
then  wonder  why  the  feed  water  does  not  show  the  same  result !  If  the 
reader  will  refer  to  Fig.  1,  in  which  A  represents  a  side  of  the  feed-water 
heater,  B  the  feed  pipe  to  the  boiler  from  the  upper  portion  of  the  heater,  C, 
D,  E,  F,  are  all  for  the  testing  of  feed  water,  and  will  be  explained  further 
on.  Fig.  3  is  a  crude,  but  simple  and  reliable,  method  of  testing  any  ther- 
mometer, and  it  is  a  very  desirable  proceeding  to  test  thermometers,  for  we 
have  found  them  varying  15°  to  20°  from  the  standard  which  we  have,  and 
always  refer  to  in  any  test  of  pressure,  or  steam,  or  for  temperature  of  feed 
water,  whenever  we  are  working  around  boilers  or  in  any  steam  work.  Take 
a  tin  can  or  pail,  anything  which  will  hold  water  three  inches  deep  or  over 
that,  and  put  it  upon  a  fire,  or  anywhere  else,  to  boil ;  when  it  is  boiling, 
then  enter  the  thermometer  bulb  into  the  water  an  inch  or  more  in  depth,  and 
notice  whether  it  records  212°  or  220°,  or  any  other  point,  and  also  notice 
that  the  water  is  kept  boiling  until  the  observation  is  complete  ;  whatever  the 
variation  is  between  212°  and  the  record  of  the  test,  remember  that  and  make 
the  allowance  in  all  future  observations  taken  with  that  thermometer. 
It  is  very  seldom  that  we  find  a  thermometer  which  shows  less  than  212°  at 
boiling. 

If  we  refer  to  Fig.  1  again,  there  is  a  cross  put  in  the  feed  pipe  from  the 
heater  to  the  boiler,  from  which  the  feed  pipe  proper  leads  off  at  B,  the  pipe 
which  is  continued  down  to  C,  branches  off  again  at  D,  having  an  outlet,  say 
one  quarter  of  an  inch  in  diameter  upon  one  side  and  one  and  one-half  inches 
upon  the  other.  We  have  found  these  arrangements  sometimes  put  upon  the 
heater  of  one  maker  by  another  who  was  desirous  of  making  a  test  of  his 
opponent's  feed-water  heater,  and  it  is  somewhat  curious  that  the  most  of 
these  tests  are  made  by  means  of  thermometers  exposed  to  the  open  air. 


266 


TWENTY  YEARS  WITH  THE  INDICATOR, 


while,  as  a  matter  of  fact,  the  heater  is  used  in  its  e very-day  work  "  under 
pressure  ;"  the  temperature  of  the  water  drawn  from  the  boiler  itself,  will  not 
be  over  212°,  if  tested  at  the  point  D  or  E,  no  matter  if  the  boiler  was  ten  feet 
distant,  and  the  pressure  80  pounds. 

We  will  now  refer  to  Fig.  2,  in  which  A  represents  the  glass  tube  of  the 
thermometer  correctly  graduated,  and  used  only  after  it  has  been  thoroughly 
tested,  D  is  a  cast-iron  plug  which  fits  into  the  top  of  the  cross,  immediately 
over  the  boiler  feed  pipe  B,  Fig.  1 ;  into  the  top  of  D  is  drilled  the  hole  for  a 
half -inch  gas-pipe  plug  B,  which  has  been  cupped  out,  and  under  it  a  piece  of 
rubber  packing,  C,  fitted.  The  holes  in  B  and  D  are  slightly  larger  than  the 
thermometer  tube,  and  the  rubber  is  punched  so  as  to  fit  close  ;  when 


Fi».2 


the  tube  has  been  put  into  place,  the  rubber  slipped  down  upon  it,  and  the 
plug,  B,  screwed  up,  so  that  the  bulb  will  be  held  below  the  crossing  of  the 
other  pipe,  we  are  ready  to  put  the  plug  into  the  top  of  the  cross  and  com- 
mence operations.  As  a  safeguard  the  cord  E  is  led  from  a  small  peg  in  each 
side  of  the  plug  through  the  ring  in  the  top  of  the  thermometer,  so  as  to  pre- 
vent its  moving  up  by  the  pressure.  In  this  disposition  of  the  thermometer 
the  boiling  point  should  always  be  left  above  the  top  of  the  plug. 

With  this  arrangement,  which  any  engineer  can  readily  fix  up  for  himself, 
it  is  perfectly  easy  to  test  correctly  and  completely  what  the  temperature  of 
feed  water  is,  which  is  passing  into  the  boiler,  and  it  can  be  done  for  fifty 
cents  beyond  the  price  of  the  thermometer,  and  these,  from  a  reliable  maker, 
will  cost  from  $1.30  to  $1.50  each.  If  there  is  an  angle  valve  in  the  feed 
near  the  boilers,  it  is  a  first-rate  place  in  which  to  put  the  thermometer  so  as 


TWENTY  YEARS  WITH  THE  INDICATOR.  267 

to  know  at  what  temperature  the  water  enters  the  boilers,  but  whenever  the 
apparatus  is  put  in,  let  the  bulb  of  the  thermometer  always  remain  in  the 
current  of  water  which  is  under  pressure.  Water  boils  at  the  level  of  the 
sea  at  212°,  and  for  each  500  feet  above  the  level  of  the  sea,  it  boils  at  one 
degree  less  than  212°  ;  never  test  steam  or  water  under  pressure  unless  you 
put  the  thermometer  into  the  current  of  moving  water  or  steam. 


LUSTEKLESS  FINISH  ON  TEMPEEING    STEEL. 


A  fine  lusterless  surface  on  tempered  steel  can  be  procured  by  either  of 
the  following  operations  :  After  the  steel  article  has  been  tempered,  it  should 
be  rubbed  on  a  smooth  iron  surface  with  some  pulverized  oil-stone  until  it  is 
perfectly  smooth  and  even,  then  laid  upon  a  sheet  of  white  paper  and  rubbed 
back  and  forth  until  it  acquires  a  fine  dead  finish.  Any  screw  holes  or  de- 
pressions in  the  steel  must  be  cleaned  beforehand  with  a  piece  of  wood  and 
oil-stone.  This  delicate,  lusterless  surface  is  quite  sensitive,  and  should  be 
rinsed  with  pure,  soft  water  only,  when  the  article  will  be  found  to  have  a 
fine,  lusterless  finish. 


PATTEEN  YAENISH. 


A  varnish  has  been  patented  in  Germany  for  foundry  purposes  and 
machinery,  which  it  is  claimed  dries  as  soon  as  put  on,  gives  the  patterns  a 
smooth  surface,  and  is  a  good  filler.  This  varnish  is  prepared  in  the  follow- 
ing manner  :  Thirty  pounds  of  shellac,  ten  pounds  of  Manilla  copal  and  ten 
pounds  of  Zanzibar  copal  are  placed  in  a  vessel,  which  is  heated  externally 
by  steam,  and  stirred  from  four  to  six  hours,  after  which  150  parts  of  the 
finest  potato  spirit  are  added,  and  the  whole  heated  during  four  hours  to  87° 
C.  This  liquid  is  dyed  by  the  addition  of  orange  color,  and  can  then  be  used 
for  painting  the  patterns.  When  used  for  painting  and  glazing  machinery,  it 
consists  of  thirty-five  pounds  of  shellac,  five  pounds  of  Manilla  copal,  ten 
pounds  of  Zanzibar  copal  and  150  pounds  of  spirit. 


268 


TWENTY  YEARS  WITH  THE  INDICATOR. 


THE  CALORIMETEB  TEST. 


RULE  FOR  MAKING  IT. 

"We  give  the  following  old  but  simple  rule  for  a  Calorimeter  test :  Take 
steam  from  main  pipe  near  boiler  with  ^-inch  pipe — the  pipe  must  be 
thoroughly  protected  by  covering  with  hair  felt ;  the  lower  end  of  pipe  should 
be  closed,  and  £-inch  holes  drilled  so  as  to  form  a  rose ;  the  holes  should  be 
close  to  bottom  of  cap,  so  as  not  to  trap  water;  the  valve  should  be  within 
easy  reach ;  a  can  (bright  tin  is  preferable)  holding  twelve  to  fifteen  pounds  of 
water  should  be  provided,  with  sufficient  opening  in  top  to  insert  steam  pipe 
and  take  temperature ;  this  also  should  be  well  protected  with  hair  felt ;  a 
small  scale,  steelyard,  01  spring  balance,  can  be  used  for  weighing ;  put  exactly 
ten  pounds  water  in  the  can,  note  its  temperature,  move  the  scale  weight  out 
one  pound,  so  as  to  have  just  eleven  pounds  water  when  test  is  complete ; 
blow  steam  through  pipe  to  free  it  of  any  water  of  condensation,  insert  pipe 
in  can,  and  when  just  one  pound  of  steam  has  been  condensed  (eleven  pounds 
water  in  can)  shut  off  steam  and  note  temperature  of  water.  The  difference 
is  the  caloric. 

This  formula  is  based,  as  all  are,  on  the  total  heat  of  steam  latent  and 
sensible,  less  the  temperature  of  water  above  zero,  and  can  be  calculated  thus : 
Latent  heat  966,  sonsible  212=1178,  less  the  temperature  of  10  pounds  water, 
which  leaves  1178 — 80=1098.  Now  we  turn  one  pound  steam  into  10 
pounds  water,  and  find  the  temperature  has  risen  from  80°  to  176°,  a  gain  of 
96°.  This  we  multiply  by  11  pounds  water,  11x96  =  1056,  nearly  equal  to 
our  1098  total  available  heat ;  100°  rise  of  temperature,  if  no  heat  had  been 
absorbed  by  the  can  containing  the  water,  would  be  dry  steam.  It  has  been 
found  by  experiment  that  96°  under  the  above  rule  is  dry  steam.  Had  the 
rise  of  temperature  been  but  80°,  the  amount  of  water  in  the  steam  would 
have  been  20  per  cent.  The  tables  approximate  closely  to  the  actual  amount 
of  water  carried  over  in  the  steam : 


OP  TEMPERATURE  OBSERVED  ABOVE  THE 
SUPERHEATED  STEAM. 

96  degrees  dry  steam. 


80 

71 

63 

54 

46 

87 

28.5 

20 

15 

11.5 


PERCENTAGE  OP  WATER  IN  STEAM. 


5  per  cent,  water. 
10 


100  all  water. 


TWENTY  YEARS  WITH  THE  INDICATOR.  269 


IKON   PAINT. 


Iron  paint,  as  it  is  termed — a  paint  composed  of  pulverized  iron  and  lin- 
seed oil  varnish — is  a  recent  German  invention,  and  is  intended  for  covering 
damp  walls,  outer  walls,  and,  in  short,  any  place  or  vessel  exposed  to  the  action 
of  the  open  air  and  to  the  weather.  Should  the  article  to  be  painted  be  ex- 
posed to  frequent  changes  of  temperature,  linseed  oil  varnish  and  amber 
varnish  are  mixed  with  the  paint  intended  for  the  first  two  coats,  without  the 
addition  of  any  artificial  drying  medium.  The  first  coat  is  applied  rather 
thin,  the  second  a  little  thicker  and  the  last  in  a  rather  fluid  state.  The 
paint  is  equally  adapted  as  weather-proof  coating  for  wood,  stone  and  iron ; 
nor  is  it  necessary  to  previously  free  the  latter  from  rust,  grease,  etc.,  a  super- 
ficial cleaning  being  sufficient. 


JOULE'S  EQUIVALENT. 


The  conversion  of  heat  into  work  is  the  main  purpose  of  the  steam  en- 
gine.  In  other  words,  we  could  not  use  coal  in  the  steam  cylinder,  and  water 
is  therefore  made  the  medium  to  convey  the  products  of  combustion,  trans- 
ferred from  coal  to  water,  through  the  steam  boiler,  and  the  steam  in  the 
fluid  state,  under  various  pressures,  passes  through  all  the  pipes,  valves, 
ports,  is  controlled  by  the  valves  so  that  it  is  more  or  less  economically  used 
according  to  their  action,  and  the  only  way  we  have  of  establishing  this  action 
for  economical  comparisons  for  the  purpose  of  ascertaining  the  power,  is  by 
means  of  the  indicator.  We  must,  therefore,  have  some  standard,  and  for  that 
purpose  frequent  reference  is  made  to  the  unit  or  equivalent.  Mr.  Joule,  at 
Cambridge,  England,  in  1845  or  '46  first  exhibited  the  apparatus,  and  at  that 
time  he  considered  that  it  required  781.5  pounds  to  equal  the  raising  of  one 
pound  of  water  1°  Fahrenheit,  while  in  another  case  it  was  slightly  increased, 
but  was  subsequently  settled  that  the  precise  equivalent  of  the  unit  of  heat 
was  772  pounds  raised  one  foot  high,  and  this  is  what  is  termed  Joule's 
equivalent. 


270  TWENTY  YEARS  WITH  THE  INDICATOR, 

Joule's  equivalent  has  been  generally  substantiated  by  scientific  research 
and  is  accepted  as  true.  It  may  be  defined  as  the  work  done  raising  one 
pound  through  one  foot,  and  is  called  either  the  foot-pound,  or  the  unit  of 
heat ;  or  the  heat  required  to  raise  the  temperature  of  a  pound  of  water  1° 
Fahrenheit,  and  is  the  equivalent  of  772  units  of  work.  When  a  pound  of 
water  at  the  temperature  of  boiling,  212°  Fahrenheit,  or  100°  Centigrade, 
when  at  the  atmospheric  pressure,  passes  into  a  state  of  steam  of  the  same 
temperature,  966.6  units  of  heat,  equivalent  to  746,215  units  of  work,  dis- 
appear, being  converted  into  internal  and  external  work. 

Mr.  Joule  also  has  announced  what  absolute  cold  was,  and  this  is  con- 
sidered proven  by  scientific  research  at  461.2°  below  zero  of  the  Fahrenheit 
scale  or  —  274°  on  the  Centigrade  scale.  The  theory  upon  which  Joule's 
equivalent  is  rested  is  that  heat  is  motion,  and  that  absolute  rest  would  be 
absolute  cold,  and  that  the  atoms  of  which  bodies  consist,  are  always  in 
motion,  and  if  they  were  brought  to  absolute  rest,  this  would  give  the  result 
which  he  first  announced,  and  which  has  generally  been  accepted  by  the  best 
authorities,  as  461.2°  below  zero,  Fahrenheit. 


COLOEING  SOFT  SOLDER  YELLOW. 


When  brass  is  soldered  with  soft  solder,  the  difference  in  color  is  so 
marked  as  to  direct  attention  to  the  spot  mended.  The  following  method  of 
coloring  soft  solder  is  given  by  the  Metallarbeiter  :  First  prepare  a  saturated 
solution  of  sulphate  of  copper  (bluestone)  in  water,  and  apply  some  of  this  on 
the  end  of  a  stick  to  the  solder.  On  touching  it  with  a  steel  or  iron  wire  it 
becomes  coppered,  and  by  repeating  the  experiment  the  deposit  of  copper 
may  be  made  thicker  and  darker.  To  give  the  solder  a  yellower  color,  mix 
one  part  of  a  saturated  solution  of  sulphate  of  zinc  with  two  of  sulphate  of 
copper,  apply  this  to  the  coppered  spot,  and  rub  it  with  a  zinc  rod.  The 
color  can  be  still  further  improved  by  applying  gilt  powder  and  polishing. 

On  gold  jewelry  or  colored  gold,  the  solder  is  first  coppered  as  above, 
then  a  thin  coat  of  gum  or  isinglass  solution  is  applied  and  bronze  powder 
dusted  over  it,  which  can  be  polished  after  the  gum  is  dry  and  made  very 
smooth  and  brilliant ;  or  the  article  may  be  electro-plated  with  gold,  and  then 
it  will  all  have  the  same  color. 

On  silverware  the  coppered  spots  of  solder  are  rubbed  with  silvering 
powder,  or  polished  with  the  brush  and  then  carefully  scratched  with  the 
scratch  brush,  then  finally  polished. 


TWENTY  YEARS  WITH  THE  INDICATOR.  271 


RECIPES  FOE  SOLDEEING  FLUID. 


One  dram  each  of  powdered  copperas,  borax  and  prussiate  of  potash ; 
one-half  ounce  powdered  sal  ammoniac  ;  3^-  ounces  fluid  muriatic  acid  ;  let  the 
mixture  cut  all  the  zinc  it  will  and  then  dilute  with  one  pint  of  water.  This 
is  something  extra  for  soldering  raw  edges  of  tin  or  galvanized  iron.  The 
above  quantity  of  fluid  costs  fifteen  cents. 

Add  granulated  zinc  or  zinc  scraps  to  two  fluid  ounces  of  muriatic  acid 
until  hydrogen  ceases  to  be  given  off;  add  one  teaspoonful  of  ammonium 
chloride ;  shake  well  and  add  two  fluid  ounces  of  water. 

Also  a  good  fluid  for  soldering  bright  tin  can  be  made  of  well-pounded 
resin  and  sweet  oil.  It  was  used  years  ago  by  the  tinners  of  Great  Britain 
for  soldering  planished  ware  made  in  those  days,  and  is  excellent  for  solder- 
ing fine  work,  silver  and  plated  ware  ;  it  can  be  wiped  off  with  a  clean  rag  and 
leave  no  stain  or  scratches. 


SAFETY-VALVE  PEOBLEMS. 


1.  Do  you  wish  to  know  the  pressure  of  the  ball  as  it  hangs  ?  Ball  weighs 
90  pounds.       Multiply  the  weight  of  the  ball  by  the  distance  in  inches  the 
weight  hangs  from  the  center  of  the  fulcrum,  say  30 ;  divide  that  by  the  dis- 
tance in  inches  from  the  center  of  the  valve  to  the  center  of  the  fulcrum,  say 
5  ;  add  the  weight  of  the  valve  and  lever  in  pounds,  say  20 ;  divide  this  by  the 
square  inches   in   the  valve,    say  20  ;  and  the   result  will  be  the  pressure  in 
pounds  on  a  square  inch  of  the  ball,  equal  to  28. 

90x30^-5  +  20-^-20^28 

2.  If  you  wish  a  certain  pressure  with  a  ball  you  have  never  used,  then 
say  the  valve  is  4  inches  in  diameter,  the  area  is  12.566.     Multiply  this  by  the 
pressure  you  want  in  pounds,  say  40 ;    subtract  from  it  the  weight  of  valve 
and  lever,  say  16 ;  multiply  this  by  the  distance  from  the  center  of  the  valve 
to  the  center  of  the  fulcrum,   say  4 ;  divide  this  by  the  weight  of   the  ball  in 
pounds,  say  80  ;  and  the  distance  in  inches  the  ball  must  be  from  the  center 
of  the  fulcrum  will  be  the  result,  as  24J. 

12.566x40— 16x4-f-80=24J. 


272  TWENTY  YEARS  WITH  THE  INDICATOR. 

3.  If  you  wish  a  ball  upon  the  lever  for  a  certain  pressure  in  pounds, 
multiply  the  area  of  the  valve  7.068  by  the  pressure  required  50  pounds,  take 
out  the  weight  of  the  valve  and  lever  ;  multiply  that  result  by  the  distance 
from  the  center  of  the  valve  to  the  center  of  the  fulcrum,  say  3  inches  ;  divide 
this  result  by  the  distance  from  where  you  put  the  ball,  21  inches,  to  the 
center  of  the  fulcrum,  and  this  will  give  you  the  weight  of  the  ball. 
7.068X50X3^21  =  50^  pounds,  weight  of  ball. 


RULE  FOR  ASCERTAINING  SIZE  OF  SAFETY-VALVE  FOR  ANY  GIVEN 

GRATE  SURFACE. 

The  required  aggregate  area  of  safety-valve  to  be  placed  upon  boilers, 
may  be  expressed  by  the  formula, 

225XG 
A=- 

P  +  8.62 

in  whicft  A  is  area  of  safety-valve  in  inches ;  G  is  area  of  grate  in  square  feet ; 
P  is  pressure  of  steam  in  pounds  per  square  inch,  to  be  carried  on  the  boiler 
above  the  atmosphere.  The  following  table  gives  the  results  of  the  formula 
for  one  square  foot  of  grate  as  applied  to  boilers  used  at  different  pressures  : 

PBESSUEES  PER  SQUARE  INCH. 

10.       20.       30.       40.       50.       60.       70.       80.       90.     100.     110.     120. 

I  I  I  I  I          I  I  I  I          I  I          I 

1.21     0.79     0.58    0.46     0.38     0.33     0.29     0.25     0.23     0.21     0.19     0.17 

(area  corresponding  to  one  square  foot  of  grate.) 

Example. — Bequired,   area  of  safety-valve  in  square  inches  for  boiler 
running  at  80  Ibs.  pressure  and  30  feet  grate  surface. 

For  1  square  foot  from  table  at  80  Ibs.— 0.25 
Square  feet  grate  surface  —  .30 


Area  of  valve  in  square-inches  =7.50 

If  a  forced  or  artificial  draft  is  used,  the  estimate  is  based  on  a  consump- 
tion of  16  Ibs.  of  fuel  for  each  square  foot  of  grate  surface. 

This  rule  was  furnished  by  the  scientific  commission  which  framed  the 
inspection  law  for  the  city  of  Philadelphia. 


Tarnished  colored  gold  articles,  it  is  said,  may  be  restored  by  the  follow- 
ing method :  Dissolve  one  ounce  of  bicarbonate  of  soda,  half  an  ounce  of 
chloride  of  lime,  and  half  an  ounce  of  common  salt,  in  about  four  ounces  of 
boiling  water.  Take  a  clean  brush,  and  wash  the  article  with  the  hot  solution 
for  a  few  seconds,  and  rinse  immediately  in  two  clean  waters.  Dry  in  warm 
sawdust,  and  finally  rub  over  with  tissue  paper. 


TWENTY  YEARS  WITH  THE  INDICATOR.  273 


WATEE  IN  THE  CYLINDER. 


It  has  now  become  generally  accepted  among  the  best  authorities  that 
the  indicator  diagram  will  show  the  water  or  presence  of  water  in  the  cylinder 
when  working.  It  must  first  be  positively  settled  that  there  are  no  leaks 
about  the  valves  or  piston  or  that  there  is  nothing  which  shall  disturb  the 
true  diagram,  for  unless  the  engine  is  in  mechanical  perfection  as  nearly  as 
possible,  the  real  reading  of  a  diagram  does  not  give  us  the  facts,  and  am- 
biguous quantities  enter  in.  We  must,  therefore,  be  sure  that  the  engine  is 
mechanically  in  first-class  condition  and  proper  order  ;  then  having  arrived  at 
the  point  of  the  stroke  where  steam  is  cut  off,  with  precision,  we  can  figure 
for  water  in  the  steam.  This  varies  considerably  with  the  conditions  under 
which  the  valves  are  working.  If  a  great  deal  of  water  is  present,  it  makes  a 
radical  difference  in  the  expansion  curve.  We  can  readily  plot  upon  an  in- 
dicator diagram  the  pressure  of  steam  with  regard  to  its  density  and  volume, 
by  reference  to  the  table  of  Properties  of  Saturated  Steam,  if  we  wish  to  £o 
so ;  but  in  doing  this,  we  have  certain  other  factors  which  must  be  taken  into 
account,  which  involve  many  figures,  and  also  points  about  which  the  best 
authorities  differ  so  widely  that  we  have  not  carried  it  out  in  this  volume ; 
that  rather  belongs  to  the  science  of  the  indicator  than  to  its  practice,  and  is 
a  point  upon  which  the  best  authorities  do  not  by  any  means  agree. 


To  cut  GAUGE  GLASSES  to  length  take  a  drill  rod,  sharpen 
the  end  and  turn  it  at  right  angles  to  rod,  like  cut,  and  harden 
the  end  without  drawing  the  temper.  Be  careful  in  hardening 
not  to  get  the  point  too  hot,  as  its  being  so  small  it  is  liable  to 
be  burned. 

Every  engineer  will  find  this  a  handy  tool. 

When  a  glass  is  to  be  cut  find  the  length,  and  with  this  tool 
cut  a  ring  around  the  inside  of  the  glass  and  it  will  usually  break 
off  square  at  that  point  at  once.  If  it  does  not,  a  little  heat 
applied  at  that  point  will  hasten,  or  if  laid  down  a  few  minutes 
it  will  crack  off. 

A  glass  cut  on  the  outside,  unless  cut  very  deep  with  a  file  or 
stone,  is  liable  to  crack  anywhere. 


274  TWENTY   YEARS  WITH  THE  INDICATOR. 


BABBITT  METAL. 


Nearly  half  a  century  ago  Isaac  Babbitt  of  Taunton,  Mass..  originated 
the  alloy  which  has  since  been  known  as  Babbitt  Metal.  It  is  highly  valued 
for  its  anti-friction  qualities  as  compared  with  other  metals.  Isaac  Babbitt 
was  a  goldsmith  by  trade  and  made  the  first  Britannia  ware  produced  in  this 
country.  He  was  honored  with  a  gold  medal  for  his  discovery  of  his  anti- 
friction alloy,  and  was  also  presented  with  $20,000  by  the  Congress  of  the 
United  States.  Below  are  several  formulas  for  preparing  Babbitt  metal  for 
different  uses  : 

WHITE    ALLOY,    OR    BABBITT    METAL. 

A — Copper 10 

Tin   72 

Antimony 18 

100 
This  alloy  is  recommended  for  high-speed  machinery  journal  boxes. 

B — Copper 1 

Tin 48 

Antimony 5 

Lead..  2 


56 

This  alloy   is   more  economical  than  the   above  and  has  a  more  greasy 
touch  than  the  first-named  above,  but  is  not  so  desirable  for  high  speed. 

C— Lead 32 

Zinc 20 

Antimony 48 

100 

This  alloy  will  resist  a  rapid  friction.      The  zinc  should  be  melted  first, 
then  add  the  other  metals. 

D— Lead 90 

Antimony 100 

This  alloy  is  suitable  for  pillow  blocks,  agricultural  or  other  slow  work- 
ing machinery. 


TWENTY  YEAES  WITH  THE  INDICATOR. 


27S 


[From  Hamilton's  Useful  Information  for  Railroad  Men.] 
USEFUL  NUMBERS  FOR  RAPID  APPROXIMATION, 


Feet  

.  .  X         .00019 

=  miles. 

Yards  

..X         -0006 

=  miles. 

Links  

..X         .22 

=  yards. 

Links 

..X         .66 

=feei 

Feet  

,  .  X        1.5 

—links. 

Square  inches  

.  .  X         -007 

=  square  feet. 

Circular      "     .  ,  

,  .  X         .00546 

it                tt 

Square  feet  

..X         .111 

=     "       yards. 

Acres  

.  .  X4840. 

a          a 

Square  yards  

..X          .0002066—  acres. 

Width  in  chains  

..X        8. 

=     "     per  mile. 

Cubic  feet  

.  .  X          .04 

=  cubic  yards. 

Cubic  inches  

.  .  X          .00058 

=     "     feet. 

U.  S.  bushels  

.  .  X         .046 

—     "     yards. 

a         a 

.  .  X       1.244 

=     "     feet. 

tt            a 

.  .  X2150.42 

=     "     inches. 

Cubic  feet  

.  .  X         .8036 

=  U.  S.  bushels. 

"      inches  

.  .  X         .000466 

—     a         a 

U.  S.  gallons  

.  .  X          .13368 

=  cubic  feet. 

a         a 

..X  231. 

=     "     inches. 

Cubic  feet  

.  .  X        7.48 

=  U.  S.  gallons. 

Cylindrical  feet  

.  .  X        5.878 

—     tt         tt 

Cubic  inches  

.  .  X         .004329 

a         a 

Cylindrical  inches  

.  .  X         .0034 

tt         it 

Pounds  

.  .  X          .009 

=cwt.  (112  Ibs.) 

Pounds  

.  .  X         .00045 

=tons  (2240  Ibs.) 

Cubic  feet  water  

.  .  X     62.5 

=lbs.  avoirdupoia 

"      inches  "   

.  .  X         .03617 

tt             tt 

Cylindrical  foot  of  water.  .  .  . 

.  .  X     49.1 

—   ..             tt 

Cylindrical  inches  of  water.  .  . 

.  .  X         .02842 

..             tt 

U.  S.  gallons  of  water  

.  .  :       13.44 

=cwt.  (112  Ibs.) 

U.  S.  gallons  of  water  

..+  268.8 

—tons. 

Cubic  feet  water  

.  .  :          1.8 

=cwt.  (112  Ibs.) 

tt            it            tt 

.  .  •      35.88 

=tons. 

Cylindrical  foot  of  water  

.  .  X       5.875 

=U.  S.  gallons. 

Column  of  water,  12"  high  ;  1 

inch  diameter 

=34  pounds. 

183,346  circular  inches  

=  1  square  foot. 

2,200  cylindrical  inches  

=  1  cubic      "k 

French  metres  

.  .  X       3.281 

=feet. 

Kilogrammes  

.  .  X        2.205 

=  avoirdupois  Ibs, 

Grammes  

.  .  X          .0022 

tt             tt 

276  TWENTY  YEARS  WITH  THE  INDICATOR. 

To  write  upon  terra-cotta  tablets,  dip  the  clay  tablet  in  milk,  with  a  few 
drops  of  acid  added,  and  then  dry.  When  this  is  done  you  can  write  upon  it 
as  easily  as  upon  paper. 


THE  PROPERTIES  OF  SATURATED  STEAM. 


In  the  tables  which  follow,  steam  is  considered  from  M.  Regnault' B 
results,  and  "  total  heat "  is  from  the  Fahrenheit  zero. 

The  bases  of  all  his  results  are,  that  the  saturated  steam  maintains  rela- 
tively density,  temperature,  and  pressure  unchangeably  to  each  other,  and  it 
naturally  follows  that  if  one  of  these  properties  are  for  any  cause  changed, 
that  the  others  also  change  in  some  fixed  ratio,  or  that  each  of  the  others 
pass  through  relative  changes  in  proportion,  so  that  all  the  factors  change 
proportionately,  and  the  basis  remains  the  same  or  unchanged. 

In  specific  heat,  water  exceeds  any  other  substance  known,  and  the 
specific  heat  of  any  body  is  the  amount  of  heat  required  to  raise  its 
temperature  1°,  taking  the  amount  of  heat  required  to  raise  the  tem- 
perature of  water  1°  (an  equal  weight)  as  the  unit.  The  specific  heat 
of  superheated  steam,  as  stated  by  M.  Regnault,  is  .48,  while  satu- 
rated steam  is  .305 ;  and  the  same  authority  states,  that  as  saturated 
steam  is  always  at  its  dew  point,  and,  if  its  density  is  maintained,  all 
the  loss  of  heat  encountered  must  be  supplied  by  its  partial  condensation, 
and,  while  it  does  not  contain  water  necessarily,  its  temperature  cannot  be 
any  higher  than  that  of  the  water  from  which  it  was  generated.  It  has, 
until  recently,  been  supposed  that  the  specific  heat  of  saturated  steam  was 
nothing,  as  it  did  not  require  an  additional  amount  of  heat  to  raise  its 
temperature,  and  it  was  also  supposed  that  the  latent  heat  gave  the  increase 
of  temperature ;  but  M.  Regnault  has  determined  differently,  and  that 
an  addition  is  required  of  .304°  to  its  total  heat  to  raise  the  temperature  one 
degree.— See  Tables  I,  II,  HI,  IV  and  V. 


8 


1.0* 


S 

. 

£     « 

5 


10  ^«  COOt  1-4  1-4 


05  Tl<  SO  (N  C«  0«  T 


<N"*«OCO-<f       T-tt-       0510       i-   «  TH 


S  05 


«o  o  <oi>E^i^^-t^-t.--t- ^-00000000  300006  5o 


co  eo  «o  «o  t  t-  z>  t-  oo  oo  oo  oo  os  o»  o»  o»  o  o  o  o 


TWENTY  YEARS  WITH  THE  INDICATOR 


279 


III. 

HYPERBOLIC  LOGARITHMS. 


No. 

Log. 

No. 

Log. 

No. 

Log. 

No. 

Log. 

No. 

Log. 

No. 

""" 

Log. 

1.05. 

.049 

2.4 

.875 

3.75 

1.322 

5.15 

1.639 

6.5 

1.872 

7.85 

2.061 

1.1 

.095 

2.45 

.896 

3.8 

1.335 

5.2 

1.649 

6.55 

1.879 

7.9 

2  067 

1.15 

.14 

2.5 

.916 

3.85 

1.348 

1     5.25 

1.658 

6.6 

1.887 

7.95 

2.073 

1.2 

.182 

2.55 

.936 

3.9 

1.361 

I     5.3 

1.668 

6.65 

1.895 

8. 

2.079 

1.25 

.223 

2.6 

.956 

3.95 

1.374 

5.33 

1.673 

6.66 

1.896 

8.05 

2.086 

1.3 

.262 

2.65 

.975 

4. 

1.386 

5.35 

1.677 

6.7 

1.902 

8.1 

2.092 

1.33 

.285 

2.66 

.978 

4.05 

1.399 

5  4 

1.686 

6.75 

1.91 

8.15 

2.098 

1.35 

.3 

2.7 

.993 

4.1 

1.411 

5.45 

1.696 

6.8 

1.917 

8.2 

2.104 

1.4 

.336 

2.75 

.012 

4.15 

1.423 

5.5 

1.705 

6.85 

1.924 

8.25 

2.11 

1.45 

.372 

2.8 

.03 

4.2 

.435 

5.55 

1.714 

6.9 

1.931 

8.3 

2.116 

1.5 

.405 

2.85 

.047 

4.25 

.447 

5.6 

1.723 

6.95 

1.939 

8.33 

2.119 

1.55 

.438 

2.9 

.065 

4.3 

.459 

5.65 

1.732 

7. 

1.946 

8.35 

2.122 

1.6 

.47 

2.95 

.082 

4.33 

.465 

5.66 

1.733 

7.05 

1.953 

8.4 

2.128 

1.65 

.5 

3. 

.099 

4.35 

.47 

5.7 

1.74 

7.1 

1.96 

8.45 

2.134 

1.66 

.506 

3.05 

.115 

4.4 

.482 

5.75 

1.749 

7.15 

1.967 

8.5 

2.14 

1.7 

.531 

3.1 

.131 

4.45 

.493 

5.8 

1.758 

7.2 

1.974 

8.55 

2.146 

1.75 

.56 

3.15 

.147 

4.5 

.504 

5.85 

1.766 

7.25 

1.981 

8.6 

2.152 

1.8 

.588 

3.2 

.163 

4.55 

.515 

5.9 

1.775 

7.3 

1.988 

8.65 

2.158 

1.85 

.612 

3.25 

.179 

4.6 

.526 

5.95 

1.783 

7.38 

1.991 

8.66 

2.159 

1.9 

.642 

3.3 

.194 

4.65 

.537 

6. 

1.792 

7.35 

1.995 

8.7 

2.163 

1.95 

.668 

3.33 

.202 

4.66 

.54 

6.05 

1.8 

7.4 

2.001 

8.75 

2.169 

2. 

.693 

3.35 

.209 

4.7 

.548 

6.1 

1.808 

7.45 

2.008 

8  8 

2.175 

2.5 

.718 

3.4 

.224 

4.75 

.558 

6.15 

1.816 

7.5 

2.015 

8.85 

2.18 

2.1 

.742 

3.45 

.238 

4.8 

.569 

6.2 

1.824 

7.55 

2.022 

8.9 

2.186 

2.15 

.765 

3.5 

.253 

4.85 

.579 

6.25 

1.833 

7.6 

2.028 

8.95 

2.192 

2.2 

.788 

3.55 

.267 

4.9 

.589 

6.3 

1.841 

7.65 

2.035 

2.25 

.811 

3.6 

.281 

4.95 

.599 

6.33 

1.845 

7.66 

2.036 

2.3 

.833 

3.65 

.295 

5. 

.609 

6.35 

1.848 

7.7 

2.041 

2.33 

.845 

8.66 

.297 

5.05 

.619 

6.4 

1.856 

7.75 

2.048 

2.35 

.854 

3.7 

.308 

5.1 

.629 

6.45 

1.864 

7.8 

2.054 

EFFECT  OF  EXPANSION  WITH  EQUAL  VOLUMES  OF  STEAM. 

The  theoretical  economy  of  using  steam  expansion  is  as  follows.    A  like  volume  of  steam  being 
expended  in  each  case,  and  expanded  to  fill  the  increased  spaces. 


Point  of 
Cutting  Off. 

Expansion 
Number. 

Mean 
Pressure 
of  Steam. 

Gain 
Per  Cent, 
in  Power. 

Point  of 
Cutting  Off. 

Expansion 
Number. 

Mean 
Pressure 
of  Steam. 

Gain 
Per  Cent, 
in  Power. 

.1 

10. 

3.302 

230. 

.5 

2. 

.693 

69.3 

.125 

8. 

3.079 

208. 

.6 

1.66 

.507 

50.7 

.166 

6. 

2.791 

179. 

•vis 

1.6 

.47 

47. 

.2 

5. 

2.609 

161. 

.666 

.5 

.405 

40.5 

.25 

4. 

2.386 

139. 

.7 

.42 

.351 

35.1 

.3 

3.33 

2.203 

120. 

.75 

.33 

.285 

22.3 

.333 

3. 

2.099 

110. 

.8 

.25 

1.223 

20.5 

.375 

2.66 

1.978 

97.8 

.875 

.143 

1.131 

13.1 

.4 

2.5 

1.916 

91.6 

.9 

.11 

1.104 

10.4 

In  this  illustration  no  deductions  are  made  for  a  reduction  of  the  temperature  of  the  steam  while 
expanding  or  for  loss  by  back  pressure. 

The  same  relative  advantage  follows  in  expansion  as  above  given,  whatever  may  be  the  initial 
pressure  of  the  steam. 


28o 


TWENTY  YJEAES  WITH  THE  INDICATOR. 


FRACTIONS  OF  INCH  EXPRESSED  IN  DECIMALS. 

Decimals. 

1-64 

=  .015625 

2-64=  1-32 

=  .03125 

3-64 

=  .046875 

4-64=  2-32=  1-16 

=  .0625 

6-64=  3-32 

=  .09375 

8-64=  4-32=  2-16=1-8 

=  .125 

10-64=  5-32 

=  .15625 

12-64=  6-32=  3-16 

=  .1875 

14-64=  7-32 

=  .21875 

16-64=  8-32=  4-16  =  2-8=1-4 

=  .25 

18-64=  9-32 

=  .28125 

20-64=10-32=  5-16 

=  .3125 

22-64=11-32 

-  .34375 

24-64=12-32=  6-16=3-8 

=  .375 

26-64=13-32 

=  .40625 

28-64=14-32=  7-16 

=  .4375 

30-64=15-32 

=  .46875 

32-64=16-32=  8-16=4-8=2-4=1-2=  .5 

34-64=17-32 

=  .53125 

36-64=18-32=  9-16 

=  .5625 

38-64=19-32 

=  .59375 

40-64=20-32=10-16  =  5-8 

=  .625 

42-64=21-32 

=  .65625 

44-64=22-32=11-16 

=  .6875 

46-64=23-32 

=  .71875 

48-64  =  24-32  =  1  2-16  =  6-8=3-4 

=  .75 

50-64=25-32 

=  .78125 

52-64=26-32=13-16 

=  .8125 

54-64=27-32 

=  .84375 

56-64  =  28-32  =  14-16  =  7-8 

=  .875 

58-64=29-32 

=  .90625 

60-64=30-32=15-16 

=  .9375 

62-64=31-32 

=  .96875 

64-64=32-32=16-16=8-8=4-4=2-2=1.00000 

THE  AMERICAN 
Thompson  Improved  Indicator 

Complete  with  Fittings 


281 


THE  AMERICAN 
Combined  Pressure  and  Recording  Gauge 


282 


THE  AMERICAN 
Dead  Weight  Gauge  Tester 

Complete  with  Fittings 


BONNER  PORTLAND 


THE  AMERICAN 

Gauge  Board  or  Frame 


284 


THE  AMERICAN 

Special  Pop  Safety  Valve 


285 


THE    AMERICAN 
SPECIALTIES 


GAUGES 

BOURDON  —  Pressure,  Vacuum,  Compound,  Combination,  Am- 
monia, Hydraulic,  Illuminated  Dial,  Pyrometer,  Automobile,  Test,  Farm 
Engine.  Altitude,  Recording.  LANE  DOUBLE  SPRING  — Locomo- 
tive and  Farm  Engine.  DUPLEX  —  Air  Brake,  Automobile,  Recording 
and  Combined  Pressure  and  Recording. 

DEAD    WEIGHT    GAUGE   TESTER. 

VALVES 

POP  SAFETY  —  Stationary,  Marine,  Portable,  House  Heater, 
Automobile. 

RELIEF  —  Cylinder,  Underwriter,  Water,  Hydraulic. 

INDICATORS 

American  Thompson  Improved. 

American  Thompson  Improved  with  Detent  Motion. 

American  Exposed  Spring  Indicator. 

American  Ideal  Reducing  Wheel. 

American  Amsler's  Polar  Planimeter. 

WHISTLES 

Plain  Steam  and  Long  Bell,  Single  Bell  Chime. 
Single  Bell  Quartet  Chime. 


Ellison's  Throttling  Calorimeter,  Test  Pumps,  Counters  —  Round 
and  Square  Case,  Clocks  —  Marine  and  Locomotive,  Water  Gauges, 
Gauge  Cocks,  Ellison's  Draft  Gauges  and  other  specialties. 


* 
Manufactured  Solely  by 

AMERICAN  STEAM  GAUGE  AND  VALVE 
MANUFACTURING  CO. 

220CAMDEN  STREET,   BOSTON,   MASS. 
New  York  Atlanta  Chicago 


286 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 

Return  to  desk  from  which  borrowed. 
This  book  is  DUE  on  the  last  date  stamped  below. 

~ 


DEC 

pCt  24  194< 

OCT2?  1950 
i  ~  1951 

L-ZC28  1950 


LD  21-100m-9,'47(A5702sl6)476 


274759 


'   Engineering 
Library 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


